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in  tfje  €it^  of  i^eto  gorfe 

^cl^ool  of  Bental  anb  (J^ral  burger? 


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RICHARDSON'S 

MECHANICAL  DENTISTRY. 


WARREN. 


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PRACTICAL  TREATISEifi,^  , 


MECHANICAL  DENTISTRY. 


JOSEPH   RICHARDSON,  M.D.,  D.D.S., 

LATE     EMERITUS     PROFESSOR     OF     THE     PRINXIPLES     OF     PROSTHETIC     DENTISTRY     IH     THE     INDIANA 

DENTAL    COLLEGE;     FORMERLY    PROFESSOR    OF    MECHANICAL    DENTISTRY    AND 

METALLURGY   IN   THE   OHIO   COLLEGE   OF    DENTAL  SURGERY,    ETC. 


SIXTH    EDITION. 


REVISED   AND    EDITED    BY 

GEORGE  W.  WARREN,  D.D.S., 

CHIEF    OF    THE    CLINICAL   STAFF,    PENNSYLVANIA    COLLEGE    OF    DENTAL   SURGERY,    PHILADELPHIA; 
AUTHOR    OF    "a    COMPEND    ON    DENTAL    PATHOLOGY    AND    DENTAL    MEDICINE,"    ETC. 


WITH  SIX  HUNDRED  ILLUSTRATIONS. 


PHILADELPHIA  : 

P.   BLAKISTON,   SON    &    CO., 

No.    I  o  I  2  Wa lnut    Street. 
1894. 


K'r\ 


y,  A 


Entered  according  to  Act  of  Congress,  in  the  year  1893,  by 

P.  BLAKISTON,  SON  &  CO., 

In  the  Office  of  the  Librarian  of  Congress,  at  Washington,  D.  C. 


Press  of  Wm.  F.  Fell  a  Co., 

1220-24  Sansom  St., 

philadelphia. 


io 


THE    MEMORY    OF   THE    LATE 

JAMES  TAYLOR,  M.D.,  D.D.S., 

FORMEKI.Y    EMERITUS    PROFESSOR   OF  THE   INSTITUTES   OF    DENTAL   SCIENCE 
IN   THE   OHIO    COLLEGE   OF   DENTAL   SURGERY, 


ACKNOWLEDGMENT    OF    PROFESSIONAL    EMINENCE 
AND    PRIVATE   WORTH, 

fhi.s  i^olunu  is  iiratefullu  inscribed, 

BY 

HIS    FORMER    PUPIL, 

THE  AUTHOR. 


NOTE. 


In  preparing  the  sixth  edition  of  this  work,  the  editor's  first 
effort  has  been  to  make  it  preeminently  practical  as  a  text-book 
for  students,  and  a  guide  for  young  practitioners.  Useless 
methods  and  obsolete  theories  have  been  eliminated,  thus 
keeping  the  dimensions  of  the  book  convenient  and  compact. 
Much  of  the  text  has  been  re-written,  notably  the  section  on 
crown-  and  bridge-work — a  volume  in  itself;  it  has  also  been 
newly  illustrated,  bringing  the  treatise  fully  up  to  the  time  of 
its  publication. 

The  editor  desires  to  acknowledge  his  indebtedness  to  the 
writings  of  Professors  Wilbur  F.  Litch,  C.  J.  Essig,  L.  P. 
Haskell,  and  Drs.  George  Evans,  James  W.  White,  Eben  F. 
Flagg,  John    Allen.  Theo.  F.  Chupein,  and    others. 

Geo.  W.  Warren, 

Philadelphia,  October  20th,  iSgj. 


PREFACE  TO  FIFTH  EDITION 


The  demand  for  a  fifth  edition  of  the  present  work,  following 
closely  upon  the  publication  of  the  one  immediately  preceding, 
affords  gratifying  assurance  of  the  profession's  recognition  of  the 
treatise  as  a  trustworthy  exponent  of  the  present  status  of  pros- 
thetic dentistry  as  illustrated  in  the  practice  and  teachings  of  its 
representative  members. 

Not  less  obviously  does  it  furnish  proof  of  an  increasing 
interest  in  a  department  of  dental  practice  that  has  amply  vin- 
dicated its  claim  to  rank  as  a  conservative  branch  of  the  healing 
art;  a  distinction  due,  in  large  part,  to  the  introduction  and 
growth  of  more  or  less  perfected  systems  of  root-crowning  and 
bridge-dentures — systems  involving  processes  of  repair  and 
methods  of  curative  treatment  that  do  not  suffer  by  comparison 
with  those  practised  at  the  chair  in  the  important  work  of  re- 
storing to  usefulness  organs  whose  natural  functions  have  been 
impaired  or  wholly  subverted  by  the  ravages  of  decay. 

It  is  a  suggestive  fact,  commended  to  the  consideration  of 
those  who  characterize  prosthetic  dentistry  as  essentially  "  me- 
chanical," and  who  seek  to  disparage  the  professional  and  scien- 
tific qualifications  necessary  to  success  in  this  department,  that 
the  results  achieved  by  the  conservative  methods  alluded  to 
have  been  reached  only  through  a  critical  study  of  tooth- struc- 
ture and  function,  a  familiar  acquaintance  with  pathological  con- 
ditions associated  with  diseased  teeth  and  implicated  tissues,  a 
comprehensive  knowledge  of  the  curative  resources  of  dental 
therapeutics,  a  broad  and  intelligent  apprehension  of  principles 
underlying  mechanical  devices,  and  a  marvelous  development 
of  ingenuity  and  manipulative  skill. 

For  obvious  reasons,  therefore,  large  space  is  given  to  the 
consideration  of  these  systems  of  crown-replacement,  the  value 

ix 


X  PREFACE    TO    FIFTH    EDITION. 

and  importance  of  which  command,  at  this  time,  general  and 
deserved  recognition.  Subjected  to  the  crucial  tests  of  time, 
and  amenable  to  the  inexorable  verdict  of  experience,  many  of 
them,  doubtless,  will  at  no  distant  day  take  their  place  "  down 
among  the  dead  men,"  while  others,  in  obedience  to  the  opera- 
tion of  laws  that  determine  the  "  survival  of  the  fittest,"  will  live 
and  take  a  fixed  place  among  other  humane  devices  that  have 
proved  lasting  benefactions  to  mankind. 

Without  indicating  specifically  the  supplemental  contributions 
incorporated  in  this  edition,  it  will  be  sufficient  to  state  that  the 
work  has  been  materially  enriched  by  the  introduction  of  special 
methods  of  substitution,  and  various  laboratory  appliances,  so 
conspicuously  meritorious  that  they  may  properly  be  said  to 
mark  an  era  in  the  development  of  prosthetic  practice. 

Joseph  Richardson. 

Terre  Haute,  Ind.,  Seplember,  i8S8. 


CONTENTS. 


Dedication,     v 

Editor's  Note, vii 

Preface, ix 

Introduction, 17 


PART    FIRST. 

METALS  EMPLOYED  IN  DENTAL  LABORATORY  OPERATIONS,  WITH 
PRELIMINARY  OBSERVATIONS  ON  EUELS,  AND  THE  VARIOUS 
APPLIANCES  USED  IN  GENERATING  AND  APPLYING  HEAT. 

CHAPTER    I. 
FUELS. 

PAGE. 

Liquid  Fuels,  Solid  Fuels,  Gaseous  Fuels, 22-31 

CHAPTER    H. 

Appliances  used  in  the  Generation  and  Application  of   Heat,  .      32-74 
Lamps;  Burners;  Blowpipes;  Supports;  Furnaces;  Heaters;  Crucibles. 

CHAPTER    HI. 

Metals  Employed  in  Dental  Laboratory  Operations, 75-8i 

Gold,  Properties  of;  Properties  of  Particular  Alloys  of  Gold. 

CHAPTER    IV. 
Refining  Gold,  Elements  Employed,  etc., 82-87 

CHAPTER   V. 

Alloys  of  Gold  for  Dental  Purposes, S8-96 

Formulas  for  Gold  Plate  Used  as  a  Base  for  Artificial  Dentures;  Clasps, 
Wire,  Stays  or  Backings,  Metal  Pins,  etc.;  Gold  Solders,  Formulas 
for;  Method  of  Reducing  Gold  to  a  Lower  or  Higiier  Siandard  of 
Fineness,  and  of  Determining  the  Carat  of  any  Given  Alloy. 

xi 


Xll  CONTENTS. 

CHAPTER   VI. 

I'AGE 

Method  of  Converting   Gold  Alloys  into  the   Required   Forms 

FOR   Dental  Purposes, 97-106 

Thickness  of  Gold  Plate  Required  as  a  Base  for  Artificial  Dentures, 
Clasps,  Backings,  etc.  ;  Reduction  of  Gold  Solders  into  Proper  Form 
for  Use ;  Method  of  Obtaining  Gold  Wire,  Constructing  Spiral 
Springs,  etc. 

CHAPTER    Vn. 

Silver,  General  Properties  of.  Alloys  of,  Refining   Alloys   of, 

ETC., IO7-I  1 1 

Reduction  of  Silver  to  Required  Forms  for  Dental  Purposes ;  Formulas 
for  Silver  Solders. 

CHAPTER   VIII. 
Platinum,  Platinoid  Metals,  and  their  Alloys, 112-116 

CHAPTER    IX. 
Aluminum,  General  Properties  and  Alloys  of, 117-120 

CHAPTER   X. 

Copper,  Zinc,  Lead,  Tin,  Antimony  and  Bismuth,  and  their  Alloys,  .  121-126 

CHAPTER   XI. 
General  Properties   of  Alloys,  and  their   Treatment   and   Be- 
havior in  the  Process  of  Compounding, 127-129 


PART  SECOND. 

ARTIFICIAL  DENTURES, 131 

CHAPTER  I. 

Treatment  of  the  Mouth  Preparatory  to  the  Insertion  of  Arti- 
ficial  Dentures,  and  Time  Necessary  to  Elapse  After  the 
Extraction  of  the  Teeth  Before  Inserting  Artificial  Den- 
tures,     132-137 

CHAPTER  II. 

Materials,  Appliances,  and  Methods  Employed  in  Obtaining  Impres- 
sions of  the  Mouth,  138-160 


CONTENTS.  Xlll 

CHAPTER   III. 

PAGE. 

Plaster  Models,  and  Manner  of  Obtaining  Same, 161-168 

CHAPTER    IV. 
Metallic  Dies  and  Counter -Dies;  Manner  of  Obtaining  ;  Essential 

Properties,    etc., 169-186 

CHAPTER  V. 

PARTIAL  DENTURES. 

Crown- AND  Bridge-Work, 187-389 

Different  Methods  and  Systems,  and  Appliances  Used  in  the  Construction 
of  Same. 

CHAPTER  VI. 

Partial  Dentures  Retained  in  the  Mouth  by  Means  of  Clasps  At- 
tached to  THE  Natural  Teeth, 390-410 

Remarks  on  the  Use  of  Clasps  ;  The  Teeth  Most  Suitable  for  Clasping ; 
Separation  of  the  Teeth  for  the  Reception  of  Clasps;  Modifications 
in  the  Form  of  Clasps  ;  Modifications  in  the  Form  of  Plates  for  Par- 
tial Dentures  Supported  by  Clasps ;  Swaging  or  Stamping  the 
Plate,  etc. 

CHAPTER  VII. 

Partial  Dentures  Supported  in  the  Mouth  by  Atmospheric  Pres- 
sure or  Adhesion;  Modifications  in  the  Form  of  the  Base, 
etc, 4H-414 

CHAPTER  VIII. 

Method  of  Obtaining  an  Antagonizing  Model  for  Partial  Den- 
tures ;  Selecting,  Arranging,  and  Antagonizing  the  Teeth  ; 
Investing,  Adjusting  Stays,  Soldering,  etc., 415-426 

CHAPTER   IX. 

ENTIRE  DENTURES, 427-446 

A  Consideration  of  the  Principles  and  Attendant  Phenomena  Involved 
in  the  Application  of  the  Forces  Utilized  as  a  Means  of  Attachment ; 
Esthetic  Requirements  in  the  Selection  and  Arrangement  of  the 
Teeth  of  Replacement ;  The  Four  Basal  Temperaments  and  their 
General  Indications ;  The  Teeth  as  Indicated  by  Temperament ; 
Temperament  in  Relation  to  the  Ttelh. 


Xiv  CONTENTS. 

CHAPTER  X. 

PAGE. 

Entire  Dentures  Attached  to  a  Swaged  Metallic  Base-plate,    .    .  447-471 
Method  of  Construction  and  Modifications  in  the  Form  of  Antagonizing 
Model,  Articulators,  etc. ;  Arranging  and  Antagonizing  the  Teeth  ; 
Forming  a  Rim  to  the  Plate;    Constructing  and  Attaching  Spiral 
Springs;  Investing,  Lining,  Soldering,  and  Finishing  the  Plate. 

CHAPTER  XI. 

Porcelain  Teeth,  Composition,  Manufacture  of,  etc. 472-477 

CHAPTER  XII. 

Uniting  Single  Porcelain  Teeth  to  each  other  and  to  a  Metallic 
Base  with  a  Fusible  Silicious  Compound,  Forming  a  Continu- 
ous Artificial  Gum  (Continuous-gum  Work), 478-507 

Different  Methods,  and  Applications  used  in  Same. 

CHAPTER  XIII. 

RuBUER  or  Vulcanite  Base,  General  Properties  OF 508-571 

Method  of  Constructing  an  Entire  Denture  in  a  Base  of  Rubber;  Arrang- 
ing the  Teeth;  Flasking;  Packing  the  Mold;  Vulcanizing;  Finishing; 
Partial  Dentures  Constructed  in  a  Base  of  Rubber;  Metallic  Clasps 
for  same;  Substituting  Plate  for  Rubber  Teeth ;  Repairing,  etc, 

CHAPTER  XIV. 

Celluloid  Base 572-606 

Composition  and  Manufacture  of;  Processes  Preliminary  to  Molding; 
Plaster  Model;  Metal  Casts;  Waxing;  Investing;  Molding,  etc. ; 
Vulcanite  Base-plate  Faced  with  Celluloid  ;   Zylonite. 

CHAPTER  XV. 

Attaching  Porcelain  Teeth  to  a  Metallic  Base  with  Rubber  or 

Celluloid 607-614 

CHAPTER  XVI. 
Cast  Metal  Base  ;  Gold  Alloy  Cast  Base 615-626 

CHAPTER  XVII. 

Defects  of  the  Palatal  Organs  and  their  Treatment  by  Artifi- 
cial Means;  Methods  of  Making  Obturators  and  Artificial 
Velums, 627-656 


A  TREATISE 


MECHANICAL   DENTISTRY. 


INTRODUCTION. 

Before  entering  upon  a  detailed  account  of  the  agencies,  pro- 
cesses and  methods  appertaining  to  the  department  of  dental 
practice  to  which  this  work  relates,  some  general  reflections 
may  not  be  inappropriate. 

It  is  not  the  purpose  of  the  author  to  unduly  magnify  the 
claims  of  prosthetic  dentistry  upon  the  regard  and  consideration 
of  the  profession.  A  just  estimate  of  the  nature  of  its  require- 
ments, and  the  momentous  results  contemplated  in  its  practice, 
as  well  as  the  abundance  and  sufficiency  of  its  resources  in  the 
accomplishment  of  its  high  and  humane  purposes,  will,  it  is 
believed,  amply  vindicate  its  importance,  its  possibilities,  and  its 
eminent  beneficence  as  a  department  of  practical  dentistry  having 
intimate  relation  to  the  necessities  of  the  unfortunate. 

The  untimely  or  premature  loss  of  the  natural  teeth  may  be 
ascribed  to  a  number  of  diverse  causes.  Multitudes  are  lost  in 
consequence  of  abuse  or  neglect,  or  the  dread  of  pain  so  com- 
monly associated  with  the  means  employed  in  their  preservation  ; 
many  from  unavoidable  accident;  and  countless  numbers  are 
sacrificed  through  the  incompetency  and  dishonesty  of  ignorant 
and  unscrupulous  parties  who,  in  one  guise  or  another,  infest  and 
prey  upon  communities. 

Nor  can  we  exclude  from  this  list   of  causes  another  source 

of  loss  which,  by  implication,  declares  the  impotence  of  the  pro- 
2  i^ 


lO  MECHANICAL    DENTISTRY. 

fession's  curative  resources  in  the  absolute  conservation  of  these 
important  organs.  Whatever  sense  of  humiliation  may  attend 
the  statement,  it  is  nevertheless  true  that  the  highest  attainable 
skill  directed  to  the  permanent  preservation  of  the  natural  teeth 
must,  in  the  very  nature  of  things,  often  prove  inadequate  and 
abortive,  for  no  proposition  is  more  broadly  or  more  generally 
recognized  b}^  intelligent  practitioners  than  that  conservative 
practice  has  its  limitations  growing  out  of  conditions  associated 
with  individual  organisms  and  environments  wholly  beyond  the 
control  of  the  operator.  Whatever  triumphs  (and  they  are 
many  and  conspicuous)  modern  conservative  dentistry  may  have 
achieved  in  the  way  of  narrowing  the  field  of  prosthetic  prac- 
tice, the  prophecy,  born  of  hope,  that  the  time  will  come  when 
the  utmost  resources  of  human  skill  will,  in  respect  of  the  teeth, 
be  able  to  exempt  mankind  wholly  from  the  penalties  of  trans- 
gressed law,  is  as  Utopian  and  delusive  as  the  faith  that  prophy- 
lactic or  preventive  medicine  will  ultimately  eradicate  every 
form  of  disease  that  at  present  afflicts  mankind.  They  are  alike 
the  idle  dreams  of  enthusiasts  and  visionaries.  Physical  infirmity, 
in  one  form  or  another,  is  the  heritage  of  the  race,  and  human 
skill,  however  well  directed  or  conscientiously  and  intelligently 
administered,  can  do  little  more  than  assuage  or  mitigate  the 
"pains  and  penalties  "  of  the  primal  curse  that  rests  upon  all. 

It  is  the  peculiar  and  distinctive  prerogative  of  prosthetic 
dentistry  to  devise  and  perfect  means  for  the  amelioration  of  the 
condition  of  those  who,  from  whatever  cause,  have  suffered  one 
of  the  gravest  forms  of  mutilation  in  the  loss  of  organs  so  essen- 
tial to  the  healthful  performance  of  many  important  functions. 
In  this  special  field  of  humane  endeavor  the  highest  order  of 
qualification  is  imperatively  demanded  for  the  complete  fulfil- 
ment of  its  diversified  and  complex  requirements.  No  one  can 
be  said  to  be  properly  equipped  for  its  duties  who  has  not  a 
more  or  less  familiar  acquaintance  with  such  of  the  several 
branches  of  Physics  and  Natural  Philosophy  as  relate  in  any 
manner  to  his  special  work,  while  an  exact  knowledge  of  the 
Anatomy,  Physiology  and  Pathology  of  the  tissues  or  structures 
in  any  way  related  to  the  substitute  is  absolutely  indispensable. 
Added  to  such  qualifications  is  the  essential  requirement  of  the 


INTRODUCTION,  I9 

highest  order  of  manipulative  skill.  But  beyond  all  these  quali-, 
fications,  and  supplementing  them,  is  that  art  culture  which  is 
the  crown  and  inspiration  of  all  perfect  work  in  every  form  of 
substitution,  and  without  which  the  best  results  of  mere  hand- 
craft are,  in  the  main,  but  little  better  than  libels  and  caricatures. 
In  no  other  department  of  practical  dentistry  is  the  art  instinct 
so  strongly  appealed  to,  or  so  imperiously  demanded  as  a  condi- 
tion of  the  highest  success.  Dr.  Eben  M.  Flagg,  in  an  essay  on 
Dental  Art,  very  aptly  says  :  "  There  is  an  element  which  enters 
into  the  conception  and  execution  of  every  branch  of  our  labor, 
and  more  or  less  forms  part  of  every  operation  that  we  are  called 
upon  to  make,  be  it  surgical,  operative  or  prosthetic.  This  ele- 
ment lightens  our  drudgery,  enlarges  our  souls,  gives  individ- 
uality to  our  work,  and  brings  satisfaction  to  ourselves  that  fully 
repays  the  time  spent  in  fulfilling  its  requirements.  It  was 
born  with  our  race,  and  has  inseparably  accompanied  every  move- 
ment that  has  brought  comfort  and  happiness  to  man.  It  has 
contributed  its  share  toward  raising  the  physician  from  a  mere 
'  bleeding,  physicking,  leeching  '  animal,  to  the  position  he  occu- 
pies to-day,  and  has  shown  the  mechanic  and  inventor  that,  if 
he  would  be  great,  he  must  be  more  than  an  artisan  ;  he  must  be 
an  artist.  This  element — the  element  of  art — whenever  it  enters 
the  field  of  human  life,  has  for  its  function  to  finish  and  render 
attractive  the  hard  labor  that  preceded  it.  Thus,  we  do  not  find 
it  in  its  full  manifestation  except  in  those  departments  of  labor 
which  have  attained  scientific  certainty." 

Among  the  unnumbered  millions  of  human  beings  who  have 
peopled  the  earth  since  the  dawn  of  time,  it  may  be  afifirmed  that 
no  two  have  been  created  with  faces  exactly  alike.  There  is  the 
same  aggregate  of  features,  and  a  pervading  general  resemblance 
of  one  person  to  another,  but  there  will  be  found  as  infinite  a 
multiplication  of  distinct  shades  of  facial  expression  as  there 
are  human  faces,  and  each  separate  shade  of  expression  charac- 
teristic of  each  one,  and  distinguishing  him  or  her  from  all  others, 
constitutes  facial  individuality.  Each  separate  feature — as  the 
eye,  the  nose,  the  mouth,  the  teeth,  facial  contour,  complexion, 
temperament,  etc. — contributes  to  this  individuality,  and  no  one 
special  feature  more,  perhaps,  than  the  teeth.     There  are  few 


20  MECHANICAL    DENTISTRY. 

more  repulsive  deformities  than  those  inflicted  by  the  loss  of 
these  organs,  and  none  more  fatal  to  the  habitual  and  charac- 
teristic expression  of  the  individual.  It  is  the  special  mission, 
as  it  is  the  first  and  highest  duty,  of  the  dentist  to  preserve  this 
individuality  intact,  and  an  equally  imperative  duty  to  restore  it 
as  perfectly  as  possible  when  impaired.  To  fulfil,  in  the  most 
perfect  manner  possible,  this  most  difficult  of  all  the  require- 
ments of  prosthetic  practice  implies  an  art  culture  that  is  com- 
petent to  interpret  the  distinct  play  of  features  associated  with 
individual  physiognomies,  to  differentiate  individual  tempera- 
ments, and  make  available  the  sculptor's  and  painter's  percep- 
tions of  the  subtle  harmonies  of  form  and  color. 

To  the  failure  or  inability  to  properly  comprehend  the  practical 
import  or  significance  of  individual  characteristics,  so  far  as  they 
find  expression  in  the  teeth,  and  the  consequent  failure  to  conform 
our  methods  of  replacement  to  the  imperative  requirements  of  art, 
may  be  fairly  ascribed  the  deserved  reproach  into  which  prosthetic 
practice  has  fallen,  and  not,  as  is  generally  charged,  to  the  em- 
ployment of  any  particular  material  or  methods  concerned  in  the 
mechanical  execution  of  the  work. 

There  is  no  material  classed  among  the  so-called  "  cheap 
bases  "  that  does  not  embody  art  possibilities  far  beyond  what  is 
being  continually  illustrated  in  general  practice.  Unquestionably 
they  are  not  the  best  for  the  purpose,  but  they  may  be  greatly 
enhanced  in  value,  and  rendered  more  deserving  of  professional 
favor,  if  utilized  in  conformity  with  the  esthetic  requirements 
imperatively  demanded  in  all  forms  of  substitution. 

There  is  an  ethical  phase  of  this  subject  which  must  enter  as 
an  element  into  the  profession's  estimate  of  the  suitableness  of 
these  inferior  forms  of  replacement — a  question  of  obligation  and 
responsibility  involving  a  problem  the  solution  of  which  should 
be  attempted  without  unreasonable  prejudice  or  unjust  discrimina- 
tion so  far  as  materials  and  methods  are  concerned.  There  are 
multitudes  in  every  community  who,  though  not  in  indigent  cir- 
cumstances, are  unable  to  secure  expensive  services  without  great 
hardship,  and  other  multitudes  who  perforce  must  suffer  lasting 
harm  and  prolonged  deformity  on  the  same  terms.  Dentistry, 
like  Medicine,  is  professedly  a  humane  calling,  and  it  would  be 


INTRODUCTION.  21 

well  to  consider  whether  the  afflicted  have  not  just  claims  upon 
the  profession's  resources  in  providing  them  with  inexpensive 
means  of  relief  Until  the  time  comes  when  the  necessities  of 
this  class  can  be  supplied  with  wholly  unobjectionable  forms  of 
substitution  at  a  cost  that  is  not  oppressive,  or  that  does  not 
altogether  deny  relief,  it  will  be  well  to  cease  indiscriminate  con- 
demnation of  materials  and  methods  which,  when  properly  con- 
sidered in  relation  to  their  yet  undeveloped  possibilities,  are  far 
from  being  unmixed  evils.  That  there  are  radical  and  inherent 
objections  to  the  use  of  vegetable  plastics  that  do  not  attach  to 
metallic  bases  is  unquestionable,  but  it  is  equally  true  that  the 
nature,  behavior,  and  proper  or  scientific  treatment  of  these  sub- 
stances have  not  been,  until  quite  recently,  well  understood  ; 
thiat  imperfect  appliances  have  heretofore  failed  to  develop  their 
best  qualities,  and,  above  all,  that  there  is  a  prevailing  disregard 
or  ignorance  of  all  esthetic  requirements  in  the  uses  to  which 
they  are  applied.  That  the  facility  they  afford  for  the  ready  con- 
struction of  substitutes  has  attracted  to  the  ranks  of  the  profes- 
sion a  mercenary  and  unscrupulous  class  of  operators,  is  as  true 
as  it  is  unfortunate.  However  powerless  the  profession  may  have 
been  in  the  past  to  check  this  evil,  the  responsibility  for  its  con- 
tinuance in  the  future  will  rest  largely  with  the  profession  itself 
There  is  a  reasonable  assurance  that  the  era  of  irresponsible 
quackery  is  fast  passing  away.  The  people  of  three-fourths  of 
the  States  of  the  Union  have,  through  their  representatives, 
generously  and  confidingly  relegated  to  the  profession  the  power 
of  providing  a  remedy  for  the  evils  of  charlatanry,  and  have,  un- 
der legal  forms,  designated  our  Colleges  and  Boards  of 
Examiners  as  the  proper  custodians  of  the  profession's  honor  and 
the  people's  interest.  A  faithful  execution  of  the  trust  reposed 
in  these  bodies  will  go  far  to  redeem  prosthetic  practice  from  the 
undeserved  reproach  brought  upon*  it  by  a  prostitution  of  its 
legitimate  resources  wholly  unworthy  of  toleration  and  utterly 
destructive  of  all  sense  of  professional  self-respect. 


PART   FIRST. 


METALS  EMPLOYED  IN  DENTAL  LABORATORY  OPERA- 
TIONS, WITH  PRELIMINARY  OBSERVATIONS  ON  FUELS, 
AND  THE  VARIOUS  APPLIANCES  USED  IN  GENERATING 
AND  APPLYING  HEAT. 


CHAPTER  I. 
FUELS. 


It  is  essential  that  the  mechanical  operator  should  have  some 
intelligent  conception  of  the  nature  and  properties  of  such  com- 
bustible substances  as  are  ordinarily  used  in  the  dental  laboratory 
for  the  generation  of  heat.  This,  and  a  somewhat  familiar 
acquaintance  with  approved  appliances  used  in  the  application  of 
heat  and  adapted  to  his  peculiar  needs,  are  indispensable  re- 
quisites to  the  successful  practise  of  the  department  of  practical 
dentistry  to  which  this  work  relates.  Only  such  heat-producing 
substances  as  are  deemed  suitable  for  dental  laboratory  operations 
will  be  considered  with  any  degree  of  particularity. 

The  general  forms  of  fuel  may  be  classified  as  Liquid,  Solid, 
and  Gaseous.  They  will  be  treated  of,  in  more  or  less  detail, 
under  these  general  heads. 

LIQUID    FUELS. 

In  connection  with  lamps  designed  chiefly  for  soldering  pur- 
poses and  vulcanizing,  the  substances  usually  employed  are 
alcohol,  gasolene  or  kerosene.  When  alcohol  is  employed,  the 
lamp  shown  in  Fig.  i  is  found  very  convenient  and  useful. 
Gasolene  is  used  in  connection  w^ith  the  Oxycarbon  Forge 
(see  page  47),  while  good  kerosene,  uncontaminated  with 
naphtha,   may  be   used  with   safety,  and   is,  in   many  cases,  a 

22 


FUELS.  23 

valuable  substitute  for  other  combustible  materials  for  general 
heating  purposes,  and  is  largely  employed  in  connection  with 
vulcanite  and  celluloid  work  by  those  unable  to  command 
the  ordinary  illuminating  gas. 

SOLID    FUELS. 

Under  this  head  are  comprehended  such  combustible  sub- 
stances as  are  used  for  fires  or  draft  furnaces,  as  wood,  char- 
coal, bituminous  and  anthracite  coal,  and  coke.  For  baking  or 
muffle  furnaces  used  in  the  construction  of  continuous-gum  work 
and  other  allied  processes,  anthracite  and  coke  are  esteemed  the 
most  suitable  on  account  of  the  high  temperatures  attainable  in 
their  use,  and  the  persistent  or  prolonged  heat  consequent  on  the 
comparatively  slow  waste  of  substance  in  the  process  of  combus- 
tion. 

"Wood,  except  when  charred,  is  wholly  unsuited  for  laboratory 
work. 

Bituminous,  or  pit  coals,  are  generally  unfit  for  the  uses  re- 
quired of  fuel  by  the  dentist,  on  account  of  the  excessive  car- 
bonaceous residue  accompanying  their  combustion,  and  are, 
therefore,  seldom  used  except  when  reduced  to  that  form  of 
mineral  charcoal  known  as  coke. 

As  charcoal,  coke,  or  a  mixture  of  the  two,  and  anthracite 
coal  are  the  heat-producing  substances  chiefly  used  in  the  pro- 
cesses of  the  dental  laboratory  requiring  the  employment  of  solid 
fuels,  they  will  be  more  particularly  described. 

Charcoal  is  the  solid  residuum  of  the  destructive  distillation 
of  wood.  It  is  obtained  by  igniting  wood,  and  then  excluding  it 
from  the  air  while  burning  ;  the  volatile  products  are  thus  driven 
off,  while  the  carbon  remains.  The  chemical  composition  of  the 
ordinary  charcoal  of  commerce  is  given  in  the  following  table,  in 
which  it  will  be  seen  to  consist  principally  of  carbon,  combined 
with  certain  volatile  constituents,  a  considerable  percentage  of 
absorbed  water,  and  but  little  ash  : — 

Carbon, 70  Nitrogen, I 

#  Hydrogen, 5  Ash, 2 

Oxygen, II  Hygroscopic  moisture,    .    .      11 

During  the  process  of  charring,  the    volatile    constituents — 


24  MECHANICAL    DENTISTRY. 

hydrogen,  oxygen  and  nitrogen — are,  in  a  large  measure,  driven 
off,  but  no  temperature  that  can  be  commanded,  and  no  time, 
however  prolonged,  will  wholly  expel  them. 

Charcoal  is  insipid  and  inodorous,  is  a  poor  conductor  of  heat 
and  a  good  conductor  of  electricity,  is  insoluble  in  water,  is  at- 
tacked by  nitric  acid  with  difficulty,  and  is  but  little  affected  by 
the  other  acids  or  by  alkalies.  Its  carbon  constituent  is  exceed- 
ingly refractory  to  heat,  and,  if  secluded  in  a  retort,  will  neither 
fuse  nor  volatilize  under  the  highest  temperature  that  can  be  pro- 
duced. This  latter  property  of  carbon,  in  connection  with  that 
of  its  comparative  non- conduction  of  heat,  makes  it  a  valuable 
ingredient  in  the  construction  of  supports  used  in  soldering, 
represented  in  the  carbon  block  and  cylinder  (Figs.  27,  28),  and 
in  the  devices  (Figs.  50,  51)  combining  crucible  and  ingot  mold. 
Charcoal  retains  the  organic  structure  of  the  wood  from  which 
it  was  produced,  except  vvhen  prepared  at  a  very  high  tempera- 
ture, when  it  becomes  a  black,  shining,  porous  mass,  resembling 
fossil  coal,  with  a  considerable  increase  in  density  and  without  a 
trace  of  organic  structure. 

When  it  is  desired  to  maintain  a  high  heat  in  a  small  compass, 
the  charcoal  best  adapted  to  the  purpose  is  that  obtained  from 
what  is  termed  liard  wood,  as  the  beech,  the  oak,  the  alder,  the 
birch,  the  elm,  etc.  A  cubic  foot  of  charcoal  derived  from  these 
woods  weighs,  upon  an  average,  from  twelve  to  thirteen  pounds, 
while  a  similar  bulk  obtained  from  soft  wood,  as  the  fir,  the  differ- 
ent kinds  of  pine,  the  larch,  the  linden,  the  willow  and  the  poplar, 
averages  only  from  eight  to  nine  pounds.*  There  is,  therefore, 
economy  in  the  use  of  the  former  when  purchased  in  bulk  ;  and 
of  this  class  the  beech-wood  charcoal  is  the  best  on  account  of 
its  greater  specific  gravity.  Charcoals  derived  from  the  hard 
woods  possess  the  additional  advantage  of  generating  a  more 
equable  and  enduring  temperature,  and  are,  therefore,  better 
adapted  to  operations  in  the  laboratory  requiring  a  prolonged 
heat.  The  more  heavy  charcoals  require  a  stronger  draft  than 
those  of  a  lighter  character,  as  a  more  generous  supply  of  oxy- 
gen is  necessary  to  their  perfect  combustion.     Charcoal  should* 


*Ure. 


FUELS. 


•^D 


be  kept  as  dry  as  practicable,  since  it  readily  absorbs  moisture 
from  the  atmosphere,  by  v/hich  its  calorific  energy  is  materially 
impaired. 

Coke. — This  substance  is  a  carbonaceous  product  obtained 
from  bituminous  coal  that  has  been  exposed  to  ignition  for  some 
time,  excluded  from  the  contact  of  air,  the  volatile  constituents 
of  the  coal,  like  those  of  wood,  having  been  driven  off  by  the 
heat.  There  are  two  different  varieties  of  this  mineral  charcoal, 
namely,  gas  coke,  obtained  from  the  retorts  of  gas  works  after 
the  gases  have  been  separated;  and  oven  coke,  which  is  made 
in  ovens  or  pits,  and  which  is  considered  by  manufacturers  as 
the  only  true  coke,  gas  coke  being  merely  cinder.  There  is  a 
marked  difference  in  the  appearance  of  the  two  kinds  of  coke, 
the  principal  part  of  that  obtained  from  gas  houses  being  of  a 
dull,  iron-black  color,  very  spongy  and  friable,  is  more  rapidly 
consumed  in  the  process  of  combustion,  and  produces  less  heat 
than  the  harder  and  more  compact  variety.  The  best  coke  for 
heating  purposes  is  the  oven  or  pit  coke,  which  has  a  steel-gray 
color,  with  somewhat  metallic  luster,  is  compact  in  structure, 
and  splits  into  pieces  having  a  longitudinal  fracture.  Whenever 
it  can  be  procured,  the  latter  should  always  be  preferred  in  con- 
nection with  the  use  of  the  baking  or  muffle  furnaces  employed 
in  the  fabrication  of  continuous-gum  work,  porcelain  teeth,  etc. 
Until  the  more  recent  substitution  of  anthracite,  the  former  was 
exclusively  employed  for  these  purposes,  and  is  in  everyway 
suitable  in  the  production  of  high  and  persistent  temperatures. 
It  is  sometimes  used  combined  with  charcoal,  but,  when  fairly 
ignited,  gives  an  augmented  and  more  lasting  heat  when  used 
alone. 

Coke  does  not  readily  ignite,  and  at  first  generally  requires 
the  admixture  of  charcoal  to  effect  its  combustion ;  it  also 
requires  a  strong  draft  to  burn  it,  but  when  thoroughly 
ignited  it  produces  an  intense  and  persistent  heat.  As  before 
stated,  it  is  the  principal  fuel  used  in  baking  mineral  teeth, 
porcelain  blocks,  and  the  silicious  compounds  employed  in  the 
construction  of  continuous-gum  work. 

Professor  Piggot,  in  his  remarks  on  the  comparative  value  of 
fuels,  observes  :     "  Practically,  for  the  purpose  of  the  chemist, 


26  MECHANICAL    DENTISTRY. 

the  best  fuel  is  charcoal  or  coke,  or  a  mixture  of  the  two.  The 
ash  of  charcoal  being  infusible,  it  passes  through  the  bars  of 
the  grate  as  a  white  powder.  Should  potash,  however,  be  in 
large  excess,  it  corrodes  the  bricks  by  forming  with  them  a 
silicate  of  potash,  which  runs  down  the  walls  and  chokes  the 
bars.  In  small  quantities  this  action  is  beneficial,  as  it  furnishes 
a  protective  varnish,  and  unites  the  bricks  and  lutes  by  forming 
a  sort  of  cement,  which  intimately  combines  with  them. 

"  Coke  contains  a  very  variable  amount  of  ash,  which  is  com- 
posed chiefly  of  oxid  of  iron  and  clay.  The  latter  is  not  fusible 
by  itself,  but  may  soften.  When  pure  it  forms  a  harmless  slag, 
which  injures  neither  the  furnace  nor  the  crucibles.  Usually, 
however,  the  oxid  of  iron  predominates.  In  this  case  the  ash 
is  very  injurious,  for  it  is  reduced  to  a  protoxid,  which  is  not 
only  fusible,  but  powerfully  corrosive  to  all  argillaceous  matters, 
so  that  both  the  crucibles  and  furnaces  suffer."* 

Anthracite. — Anthracite  is  the  most  condensed  variety 
of  mineral  coal,  containing  the  largest  proportion  of  carbon  and 
the  smallest  quantity  of  volatile  matter.  With  the  exception  of 
the  diamond,  it  is  the  purest  form  of  carbon  in  its  natural  state. 
The  best  specimens  contain  95  per  cent,  carbon,  but  the  average 
production  of  the  purest  beds  of  this  coal  will  not  exceed  90  per 
cent.,  and  generally  not  more  than  80  to  87  per  cent,  carbon. 
The  volatile  matter  in  the  dense,  hard  varieties,  is  almost  exclu- 
sively water  and  earthy  impurities,  but  in  common  varieties  the 
volatile  portion  consists  of  water,  hydrogen,  oxygen,  and  nitro- 
gen, while  the  ash  or  incombustible  matter  contains  oxid  of 
iron,  iron  pyrites,  silica,  alumina,  magnesia,  lime,  etc.  Anthra- 
cite which  contains  only  80  per  cent,  carbon,  with  20  per  cent, 
water  and  incombustible  matter,  is  the  lowest  grade  of  commer- 
cial coal,  and  of  little  value  as  fuel. 

■  The  general  features  and  fractures  of  hard  anthracite  are 
peculiar  and  noticeable  to  the  common  observer.  They  are 
massive,  hard,  dense,  amorphous  or  conchoidal  in  fracture,  with 
fine,  sharp  edges  when  broken,  and  a  rich  satin  or  an  iron-black 
sub-metallic    luster.     With    some    local    exceptions    the    softer 

*"  Dental  Chemistry  and  Metallurgy,"  p.  274. 


FUELS,  27 

varieties,  both  red-  and  white-ash  (by  which  name  the  Pennsyl- 
vania anthracite  cor.ls  are  generally  known),  are  less  massive, 
hard  and  dense,  more  regular  and  cubical  in  fracture,  and, 
exclusive  of  the  upper  red-ash  beds,  less  rich  and  lustrous. 

Anthracite  coals,  in  greater  or  less  abundance,  and  of  varying 
qualities,  are  found  in  several  of  the  States  and  territories  of  the 
Union,  namely,  in  Pennsylvania,  Massachusetts,  Rhode  Island, 
Virgina,  Arkansas,  Oregon,  and  in  New  Mexico  and  Sonora. 
Of  the  European  anthracite  fields,  exclusive  of  those  in  Wales, 
England,  the  most  prolific  and  largely  developed  are  those  in 
France,  while  others  of  more  limited  production  are  found  in 
Spain,  Portugal,  Germany,  Austria  and  Norway.  Anthracite 
also  exists  in  Persia,  India,  China  and  in  South  America.  The 
most  prominent  anthracite  fields  of  the  world,  however,  are 
those  of  Pennsylvania  and  South  Wales,  which  produce  nine- 
tenths  of  the  quantity  used.  The  developed  coal  fields  of  the 
world  embrace  an  area  of  about  350,000  square  miles,  of  which 
over  300,000  are  in  the  United  States,  exclusive  of  lignite. 
About  2000  square  miles  of  this  entire  area  contain  anthracite, 
of  which  half  is  in  the  United  States,  including  the  somewhat 
doubtful  New  England  coal  fields.  The  entire  coal  production 
of  the  world  in  1871  was  between  225  and  250  million  tons,  of 
which  England  produced  no  millions  and  the  United  States  41 
millions.  About  20  millions  of  the  entire  amount  was  anthra- 
cite, of  which  15  million  tons  were  produced  in  Pennsylvania, 
and  the  remainder  in  South  Wales,  France  and  other  countries. 

The  first  authentic  account  which  we  find  of  the  use  of 
anthracite  in  the  United  States  was  in  1768-69,  when  it  was 
used  by  two  blacksmiths  from  Connecticut,  named  Gore.  It 
did  not,  on  account  of  the  difficulty  of  making  it  burn,  come 
into  use  for  domestic  purposes  till  1808,  when  Judge  Fell  suc- 
ceeded in  burning  "  stone  coal  "  in  a  grate  of  his  own  construc- 
tion. This  was  probably  the  first  successful  use  of  anthracite 
for  general  purposes  in  the  world.  So  imperfectly  were  the  pro- 
perties of  this  fuel  understood,  and  so  little  known  of  its  proper 
management,  that  four  years  later.  Col.  Shoemaker,  who  had 
disposed  of  several  loads  of  it  to  parties  in  Philadelphia  who 
were  unable  to  burn  it,  was  arrested,  upon  a  writ  obtained  from 


28  MECHANICAL    DENTISTRY. 

the  city  authorities,  as  an  impostor  and  swindler,  who  had  sold 
them  rocks  for  coal. 

Prof.  H.  D.  Rogers  explains  the  formation  of  anthracite  by 
supposing  it  to  be  the  result  of  altered  bituminous  coal  meta- 
morphosed by  intense  heat,  and,  of  course,  by  heat  induced 
subsequent  to  the  formation  of  the  bituminous  beds  ;  and  he 
further  explains  the  escape  of  the  volatile  portion  of  the  latter 
as  gas  through  cracks  and  openings  caused  by  the  plication  of 
the  anthracite  strata.  This  plication  follows  closely  the  general 
type  of  the  paleozoic  rocks,  which  are  intensely  crushed  and 
folded  near  the  contact  of  their  edges  with  the  igneous  or 
granitic  rocks,  and  much  less  plicated  and  distorted  in  a  western 
direction.  This  theory,  though  natural  and  ingenious,  is  con- 
troverted by  others  who  contend  that  anthracite  is  not  a  meta- 
morphosis of  bituminous  coal,  but  as  much  a  normal  creation  as 
the  bituminous  variety  itself,  from  a  combination  of  its  constitu- 
ents under  superior  heat,  however  the  original  elements  were 
produced. 

The  particular  mineral  fuel  under  consideration  has  been 
treated  of  here  somewhat  at  length,  for  the  reason  that  it  is 
being  more  generally  employed  of  late  years  by  the  dentist,  not 
only  for  refining  and  general  heating  purposes,  but  more  especi- 
ally in  those  important  processes  of  the  dental  laboratory  in 
which  more  or  less  refractory  silicious  substances  requiring  a 
high,  uniform  and  prolonged  heat,  are  employed  in  compound- 
ing body  and  gum  enamels,  in  baking  mineral  teeth,  and  in  the 
construction  of  continuous-gum  work.  For  the  latter  especially, 
it  is  preferred  by  many  to  coke,  in  connection  with  solid  fuel 
furnaces. 

Owing  to  the  difficulty  of  igniting  anthracite,  it  is  customary 
to  mix  with  it  at  first  about  an  equal  quantity  of  charcoal.  Its 
proper  combustion  after  ignition,  when  burned  alone,  requires  a 
strong  draft,  which  is  ordinarily  attainable  in  use  of  the  ordi- 
nary draft  or  muffle  furnace  properly  connected  with  a  suit- 
able flue.  Under  conditions  that  insure  more  or  less  complete 
combustion,  the  chief  of  which  is  a  generous  supply  of  oxygen, 
anthracite  will  yield  a  higher  temperature  than  any  other  kind 
of  solid  fuel.     The  blast  furnace  is,  therefore,  best  adapted  to 


FUELS.  29 

this  end,  though  for  all  ordinary  purposes  requiring  heat  in  the 
dental  laboratory  the  ordinary  chimney  draft  will  be  sufficient. 
To  recapitulate  somewhat,  it  may  be  said,  not  only  in  reference 
to  anthracite,  but  to  the  other  solid  fuels  mentioned,  that  in 
order  that  the  greatest  amount  of  heat  may  be  generated,  it  is 
necessary  that  the  conditions  essential  to  their  most  perfect  com- 
bustion should  be  strictly  observed;  these,  as  before  stated,  have 
reference  mainly  to  an  unobstructed  circulation  of  air  in  order 
that  oxygen  may  be  freely  supplied  to  them.  To  this  end  the 
furnace  should  be  kept  clean,  the  bars  of  the  grate  unbroken, 
and  a  good  draft  obtained.  The  condition  in  which  the  fuel 
is  applied  will  also  modify  the  results.  Thus,  for  example,  if 
the  lumps  are  too  large,  they  will  absorb  heat,  and  caloric  will 
be  lost;  if  too  small,  they  will  be  too  rapidly  consumed.  It  is 
essential,  also,  to  have  the  fuel  as  free  as  possible  from  dust  and 
dirt,  as  these  fine  particles  in  any  considerable  quantities  obstruct 
the  draft,  and  prevent  a  thorough  ignition  of  the  mass.  Coke, 
especially,  should  be  preserved  clean,  and  should  be  broken  into 
fragments  not  larger  than  an  inch  or  an  inch  and  a  half  in  diam- 
eter, and,  as  nearly  as  possible,  in  the  form  of  blocks  or  cubes, 
as  these  leave  more  open  spaces  for  the  free  circulation  of  air. 

GASEOUS     FUEL. 

Illuminating  Gas. — The  ordinary  illuminating  gas,  derived 
from  the  destructive  distillation  of  bituminous  coals,  is  a  form  of 
fuel  that,  of  late  years,  is  rapidly  supplanting  the  use  of  the  liquid 
and  solid  varieties  for  heating  purposes  in  the  dental  laboratory. 
The  introduction  of  gas,  for  the  uses  indicated,  marks  an  era  in 
prosthetic  practice,  so  far  as  the  application  of  heat  for  metallurgic 
purposes  is  concerned,  in  which  inventive  genius  has  been  indus- 
triously and  successfully  employed  in  devising  and  perfecting  ap- 
pliances designed  to  obviate  entirely  the  necessity  of  employing 
other  forms  of  fuel  heretofore  used,  and  which  are,  in  many  re- 
spects, inconvenient  and  objectionable.  So  fruitful  have  been  these 
later  devices  in  meeting  the  necessities  of  the  dental  metallurgist, 
and  so  reasonably  certain  is  it  that  more  extended  experiments 
in  the  construction  of  furnaces  adapted  to  this  mode  of  producing 
heat  will,  in  the  near  future,  meet  all  the  requirements  of  ceramic 


30  MECHANICAL    DENTISTRY. 

art,  as  applied  to  dental  prosthetics,  that  it  may  be  confidently 
predicted  that  all  solid  fuels  for  these  purposes  will  be  wholly 
banished  from  the  laboratory  wherever  gas  can  be  commanded 
for  the  generation  of  heat.  The  latter,  intermixed  with  atmo- 
spheric air  in  proper  proportions,  and  used  in  connection  with 
burners  and  furnaces  of  suitable  construction,  is,  in  all  essential 
respects,  preferable,  since  it  is  comparatively  free  from  dirt  and 
smoke,  and  is  capable  of  producing  a  rapid,  equable  and  intense 
heat,  which  is  completely  under  the  control  of  the  operator  as 
respects  duration  and  the  degree  of  temperature  required  for  any 
given  operation. 

Natural  gas  has,  until  recently,  been  obtained  only  in  very 
limited  quantities.  There  are  many  localities  where  combustible 
gases  have  long  been  known  to  issue  from  the  earth.  Gas  has 
been  used  in  China  for  centuries,  conveyed  in  bamboo  tubes 
from  fissures  in  salt  mines,  in  excavations  from  1200  to  1600  feet 
in  depth.  Near  the  Caspian  Sea,  in  Asia,  there  are  several  so- 
called  eternal  fires  caused  by  gas  issuing  from  the  soil.  In 
parts  of  New  York  it  issues  from  bituminous  limestone  inter- 
spersed among  the  slates  and  sandstones  of  the  Portage  group ; 
but  the  most  prolific  sources  of  natural  gas  are  in  the  coal  regions 
of  western  Pennsylvania,  where  rapidly  multiplying  wells  are 
yielding  almost  unlimited  supplies  of  this  light  and  heat-producing 
combustible,  and  which,  in  some  of  the  larger  cities,  is  being 
utilized  not  only  for  illuminating  purposes,  but  for  fuel  in  many 
of  the  manufacturing  establishments. 

The  chief  supplies  of  illuminating  gas,  however,  are  derived 
from  the  destructive  distillation  of  various  grades  of  bituminous 
coal,  and,  to  a  more  limited  extent,  from  wood,  peat,  resin, 
petroleum,  oils  and  fats,  and  from  water  and  coke.  As  the  gas 
used  in  the  dental  laboratory  for  the  generation  of  heat  is  the 
common  house  illuminating  gas  obtained  from  coal,  this  variety 
only  will  be  treated  of  in  this  place. 

Bituminous  coals,  such  as  English  cannel  and  boghead  coals, 
Ohio  cannel,  and  the  coking  coals  of  Pennsylvania,  Maryland 
and  Virginia,  are  commonly  used  in  the  manufacture  of  illumin- 
ating gas.  When  bituminous  coal  is  heated  to  redness  in  the 
presence  of  air,  it  is  principally  converted  into  gases  which  unite 


FUELS.  3 1 

with  oxygen  ;  but  if  air  is  excluded,  as  when  the  coal  is  con- 
fined in  retorts,  the  gaseous  products,  unable  to  unite  with 
oxygen,  may  be  collected  in  receivers  and  burned  in  tubes.  The 
products  of  the  destructive  distillation  of  bituminous  coal  con- 
sists of  a  great  number  of  gases,  liquids  and  solids,  which  may 
be  conveniently  included  under  the  following  heads,  according 
to  an  analysis  by  Bunsen  : — 

Coke, 68.93  Olefiant  gas, 0.78 

Tar 12.23  Sulphuretted  hydrogen,    .    0.75 

Water,      7.40  Hydrogen, 0.50 

Marsh  gas, 7.04  Ammonia, O.I 7 

Carbonic  oxid, 1. 1 3  Nitrogen, 0.03 

Carbonic  acid, 1.07 

The  illuminating  power  of  the  gas  may  be  regarded  as  de- 
pending principally  upon  the  amount  of  olefiant  gas  (heavy 
carburetted  hydrogen)  which  it  contains,  the  bulk  of  other 
gases  being  carriers  rather  than  light-producers.  The  olefiant 
gas  is  separated  by  ignition  into  marsh  gas  (light  carburetted 
hydrogen)  and  carbon,  the  solid  particles  of  which  become 
incandescent  and  emit  white  light,  which  is  observed  in  the 
luminous  cone  of  a  gas  flame,  and  which  has  the  same  constitu- 
tion as  that  of  a  candle.  The  luminosity  of  a  gas  flame  depends 
both  upon  the  percentage  of  heavy  hydrocarbons  it  contains 
and  the  amount  of  atmospheric  air  or  oxygen  mixed  with  it. 
With  the  admixture  of  air  or  oxygen,  the  illuminating  power  of 
the  gas  is  diminished,  while  there  is  at  the  same  time  increased 
evolution  of  heat.  This  fact  is  of  interest  and  value  to  the 
dentist,  since  it  underlies  the  construction  of  all  the  modern 
forms  of  heating  appliances  made  on  the  principle  of  the  Bunsen 
burner,  which  provides  for  intermingling  currents  of  atmospheric 
air  and  gas.  Oxygen  thus  applied  to  the  gas  jet,  and  combining 
with  the  carbon  at  the  moment  of  ignition,  greatly  augments  the 
heat  of  the  flame,  while  the  latter  becomes  almost  non-luminous. 

Oxy-Hydrogen  Gas. — A  combination  of  nitrous  oxid  and 
illuminating  gas  has  been  used  of  late  in  the  dental  laboratory 
with  highly  satisfactory  results,  forming  practically  an  oxy- 
hydrogen  flame  of  great  heating  power.  (See  Dr.  Knapp's  oxy- 
hydrogen  blowpipe,  page  48.) 


CHAPTER  II. 

APPLIANCES   USED    IN    THE  GENERATION    AND  APPLICATION 

OF  HEAT. 

The  modes  of  generating  heat,  and  the  appliances  used  in  its 
application  to  the  various  mechanical  processes  of  the  dental 
laboratory,  will  require  more  or  less  detailed  descriptions  of  the 
several  agencies  employed  for  these  purposes.  These  relate  to 
Lamps,  Burners,  Blowpipes,  Supports,  Crucibles,  and  Furnaces. 
As  full  a  description  of  these  several  appliances  will  be  given  as 


Fig.  I. 


is  compatible  with  the  scope  of  the  present  work.  The  agencies 
employed  in  the  generation  and  application  of  heat  alluded  to 
under  the  head  of  lamps,  burners,  supports,  and  blowpipes,  are 
such  as  are  used  chiefly  in  soldering,  one  of  the  most  important 
and  not  always  the  least  difficult  processes  of  the  dental  labora- 
tory, while  furnaces  are  largely  used  for  melting  and  refining 
purposes,     compounding    body    and    gum     materials,    baking 

32 


GENERATION    AND    APPLICATION    OF    HEAT. 


33 


Fig.  2. 


porcelain  teeth,  and  in  constructing  continuous-gum  work. 
Heaters  are  adapted  to  a  variety  of  purposes  requiring  moderate 
temperatures,  as  melting  some  of  the  more  fusible  metals, 
warming  water,  heating  plaster  molds  preparatory  to  packing 
plastic  substances,  etc. 

Lamps. — For  all  the  minor  operations  of  the  laboratory 
requiring  the  application  of  moderate  degrees  of  heat  in  the  use 
of  either  the  mouth  or  the  simpler  forms  of  bellows  blowpipe, 
an  ordinary  alcohol  lamp  or  the  gasolene  furnace  described  on 
page  62  will  be  found  serviceable  and  efficient.  When,  how- 
ever, gas  can  be  commanded,  it  is  preferable  to  the  oils  or 
alcohol  for  heat-producing  purposes,  on  account  of  its  greater 
convenience  and  freedom  from  accident. 

Burners, — The  ordinary  gas  flame  is  unsuitable  for  soldering 
or  other  operations,  by  reason  of  the  carbonaceous  residue  with 
which  it  is  constantly  charged.  This  source  of  uncleanliness 
may  be  gotten  rid  of  by  an  admixture  of  air  with  the  gas  flame. 
This  intermingling  of  gas  and  air  currents 
for  the  purpose  of  augmenting  the  heat  of 
the  gas  flame,  and  of  rendering  it  in  other 
respects  more  suitable  for  general  metal- 
lurgic  purposes,  was  first  practised  by 
Bunsen,  a  distinguished  Gernian  chemist, 
by  means  of  a  simple  contrivance  repre- 
sented in  Fig.  2.  All  modern  heat  pro- 
ducing appliances  usually  denominated 
Bunsen  burners  utilize  the  same  principle 
in  the  generation  of  heat,  and  differ  only 
in  mechanical  construction  from  Bunsen's  original  device. 

A  very  simple  contrivance  embracing  the  principle  of  the 
Bunsen  burner,  is  shown  in  Fig.  3.  A  represents  an  ordinary 
gas  burner  attached  to  a  circular  cast-iron  base,  with  a  stationary 
tube,  C,  entering  near  the  bottom,  for  the  supply  of  gas.  B  is  a 
hollow  cylinder  of  sheet  brass  or  copper,  the  lower  half  of  which 
is  perforated  with  small  holes  for  the  admission  of  air.  This  is 
placed  on  the  burner,  the  perforated  end  fitting  over  the  central 
portion,  leaving  something  of  a  space  above,  between  the  burner 
and  cylinder,  for  the  free  circulation  of  air.  The  cylinder,  when 
3 


34 


MECHANICAL    DENTISTRY. 


in  place,  should  extend  two  inches  or  more  above  the  tip  of  the 
burner.  The  gas  is  supplied  through  a  flexible  rubber  tube 
connected  with  the  stem  of  the  burner,  and  connected  at  the 
other  end  with  any  ordinary  gas  burner  conveniently  located  in 
the  laboratory.  For  soldering  small  pieces,  and  for  many  other 
purposes  requiring  a  ready  and  manageable  heat,  the  author 
has  used  this  simple  appliance,  with  great  satisfaction,  for  many 
years. 

To  obtain  a  flame  of  greater  volume  than  is  possible  with  the 
burner  just  described,  a  Bunsen   burner  may  be  constructed  in 


Fig. 


the  manner   described   by   Prof.  Essig  in  his   work   on   Dental 
Metallurgy. 

This  consists  in  attaching  to  the  base  of  an  ordinary  Bunsen 
burner  (Fig.  4),  such  as  is  sold  at  the  dental  depots,  a  piece  of 
brass  tubing  six  inches  in  length  by  one  and  a  quarter  inches  in 
diameter.  Over  the  top  of  this,  in  order  to  properly  spread  the 
flame,  a  piece  of  fine  wire  gauze  is  fastened,  by  means  of  a  ring 
of  sheet  brass  one-quarter  of  an  inch  in  width.  Gas  is  sup- 
plied in  the  same  manner  described  in  connection  with  Fig.  3. 
This  contrivance,  while  it  fully  meets  the  general   requirements 


GENERATION    AND    APPLICATION    OF    HEAT. 


35 


of  the  operator,  is  especially  adapted  to  drying  and  heating  up 

large  pieces  before  soldering,  and  for  melting  alloys  of  gold 

and  silver  in  considerable  quantities. 

Fig.  5. 


Fig.  4. 


Fig.  6. 


A  compact  and  convenient  burner  for  general  laboratory  uses 
is  represented  in  Fig.  5.  It  is  especially  useful  in  "waxing  up" 
a  base  plate,  heating  water,  vulcanizing,  and  other  minor  opera- 
tions requiring  a  moderate  and  easily-graduated  heat. 


36  MECHANICAL    DENTISTRY. 

Another  heating  apparatus  of  recent  introduction,  designed,  in 
part,  for  soldering  with  the  use  of  blowpipes,  is  represented  in 
Fig.  6.  It  is  called  the  "  Duplex  Burner,"  and  will  be  found  very- 
convenient  for  laboratory  use.  In  addition  to  the  usual  Bunsen 
burner,  a  large  flame  for  the  blowpipe  can  be  had  by  rotating  the 
upper  portion  upon  the  base.  A  small  jet,  when  once  lighted, 
ignites  either  flame,  so  that  it  is  always  ready  for  use. 

There  are  many  other  varieties  of  these  heating  appliances  con- 
structed on  the  principle  of  the  Bunsen  burner,  but  it  is  not 
deemed  essential  to  further  multiply  them  in  this  place. 

BLOWPIPES. 

Following  the  descriptions  of  lamps  and  burners  given  in  the 
preceding  pages,  it  would  seem  appropriate  to  consider  next  the 
various  forms  of  blowpipes  used  in  the  application  of  the  heat 
produced  by  means  of  the  appliances  named. 

Various  modifications  in  the  form  of  the  blowpipe  have  been  in- 
troduced from  time  to  time,  and  are  named  according  to  the 
means  used  to  produce  the  blast,  as — month,  bclloivs,  self-acting 
or  spirit,  and  the  Gasolene  or  "Oxy-carbon"  blowpipe. 

In  addition  to  the  varieties  mentioned,  there  are  others,  used 
in  producing  extreme  degrees  of  heat,  as  the  "  oxygen  blowpipe," 
with  which  the  flame  is  blown  with  a  jet  of  oxygen  ;  and  another, 
with  which  the  two  gases,  oxygen  and  hydrogen,  are  burned, 
called  the  "  oxy-hydrogen  blowpipe."  The  latter  is  capable  of 
producing  a  heat  that  immediately  fuses  the  most  refractory  sub- 
stances, as  quartz,  flint,  rock-crystal,  plumbago,  etc.  With  it 
gold  is  volatilized  and  iron  rapidly  consumed  when  placed  in 
the  flame;  while  platinum,  next  to  iridium  the  most  infusible  of 
all  known  metals,  has  been  melted  in  quantities  exceeding  one 
hundred  ounces  by  means  of  this  powerful  instrument.  As, 
however,  these  blowpipes  are,  for  the  most  part,  of  no  special 
practical  utility  in  the  dental  laboratory,  reference  will  be  had  only 
to  the  one  recently  introduced  by  Dr.  Knapp,  of  New  Orleans, 
La.  Nor  is  it  deemed  necessary  to  embrace  descriptions  of  spirit 
blowpipes,  as  they  have  fallen,  of  late  years,  almost  wholly  into 
disuse. 


GENERATION    AND    APPLICATION    OF    HEAT,  37 

MOUTH    BLOWPIPE, 

This  instrument  has  been  long  in  use,  is  simple  in  its  form  and 
construction,  and,  for  general  use  in  the  application  of  moderate 
degrees  of  heat,  is  both  convenient  and  economical.  Those 
accustomed  to  its  use  are  enabled  to  produce  a  continuous  blast 
of  considerable  force,  and  soon  acquire  the  facility  of  regulating 
the  heat  produced  with  equal  if  not  greater  precision  than  can  be 
readily  attained  in  any  other  way. 

The  most  simple  form  of  the  mouth  blowpipe  is  shown  in  Fig. 
7.  It  consists,  usually,  of  a  plain  tube  of  brass,  larger  at  the  end 
applied  to  the  mouth,  and  tapering  gradually  to  a  point  at  its 
other  extremity,  the  latter  being  curved  and  tipped  at  the  point 
with  a  conical-shaped,  raised  margin,  to  protect  it  from  the  action 


Fin.  7. 


of  the  flame;  the  caliber  of  the  instrument  terminates  here  in  a 
very  small  orifice.  The  point  of  the  instrument,  as  well  as  that 
part  of  it  received  into  the  mouth,  is  sometimes  plated  with  a  less 
oxidizable  metal  than  brass,  as  silver  or  platinum.  The  stem  is 
generally  from  twelve  to  twenty  inches  in  length,  and  the  mouth 
extremity  from  one-half  to  three-fourths  of  an  inch   in  diameter. 

In  operations  requiring  protracted  blowing,  a  somewhat  differ- 
ent form  of  the  instrument  will  be  required,  owing  to  the  accumu- 
lation of  moisture  within  the  tube,  which,  being  forcibly  expelled 
from  the  orifice,  spurts  upon  whatever  is  being  heated  and  inter- 
rupts the  blast;  also,  on  account  of  the  fatigue,  which  in  process 
of  time  renders  the  muscles  of  the  mouth  and  face  engaged  in 
the  act  to  a  great  extent  powerless. 

The  difficulties  rhentioned  may  be  obviated,  in  a  great  meas- 
ure, by  applying  the  form  of  blowpipe  represented  in  Fig.  8.  To 
the  mouth  extremity  is  attached  a  circular  concave  flange  or 
collar  which  receives  and  jupports  the  lips.     To  the  shaft,  near 


38  MECHANICAL    DENTISTRY, 

its  curved  extremity,  is  adjusted  either  a  spherical  or  cylindrical 
chamber  which  collects  and  retains  the  moisture  as  it  forms 
within  the  pipe.  By  allowing  that  part  of  the  tube  connected 
with  the  curved  end  to  pass  part  way  into  the  chamber,  a  basin 
is  formed  at  the  depending  portion  of  the  latter,  which,  by  col- 
lecting the  fluids,  will  effectually  prevent  them  from  overflowing 
and  passing  into  the  tube  beyond. 

Thomas    Fletcher,  of  Warrington,  England,  has    introduced 

Fig.  8. 


modifications  in  the  construction  of  mouth  blowpipes  which  are 
unquestionably  improvements  upon  the  simpler  forms  just  de- 
scribed. One  form,  styled  the  hot-blast  mouth  blowpipe,  is 
shown  in  Fig.  9.  The  improvement  in  this  instance  consists  in 
coiling  the  air-tube  into  a  light  spiral  over  the  point  of  the  jet. 
This  coil  takes  up  the  heat  which  would  otherwise  be  wasted, 
and  utilizes  it  by  heating  the  air  in  its  passage.  It  is  claimed  that 
with  the  use  of  this  instrument  much  higher  temperatures  are 


Fig.  9. 


reached  than  is  possible  with  the  ordinary  blowpipe,  and  that 
with  the  same  amount  of  blowing  nearly  double  the  work  is 
accomplished,  while,  if  a  high  heat  is  not  required,  the  labor  of 
blowing  is  reduced  in  proportion.  A  similar  form  of  instrument 
(Fig.  10)  is  made  with  a  hard-rubber  mouth-piece. 

Another  form  of  mouth  blowpipe  by  the  same  inventor  is 
exhibited  in  Fig.  ii.  It  will  be  seen  to  be  wholly  unlike  any 
mouth  blowpipe  yet  devised,  and  admits  of  great    latitude  of 


GENERATION    AND    APPLICATION    OF    HEAT. 


39 


movements  in  the  application  of  heat.  This  form  of  the  mouth- 
piece is  especially  adapted  to  continued  blowing  without  strain 
on  the  lips,  while  the  opening  is  well  under  the  control  of  the 
tongue.  The  blowpipe  proper  is  held  as  a  pencil,  the  chamber 
collecting  condensed  moisture  and  preventing  the  passage  of 
heat  up  to  the  end.  The  instrument  can  be  readily  changed 
from  a  cold-  to  a  hot-blast  blowpipe  by  substituting  the  coil  (b) 
for  the  plain  jet  or  tip. 

Fig.  io. 


There  are  other  allied  forms  of  the  mouth  blowpipe,  but  as 
they  are  constructed  more  especially  for  chemical  examinations 
or  analyses,  and  as  they  possess  no  advantages,  for  dental  pur- 
poses, over  those  already  mentioned,  a  description  of  them  is 
not  necessary. 

Mechanism  Involved  in  the  Act  of  Producing  a  Contin- 
uous Blast  with  the  Mouth  Blov^,'pipe. — As    a   steady,    con- 


FlG.   II. 


tinuous  current  of  air  from  the  blowpipe  is  preferable  to  the 
interrupted  jet  in  all  those  operations  where  it  is  desired  to 
produce  a  steadily  augmenting  heat,  the  following  remarks 
explanatory  of  the  method  of  producing  it  are  subjoined,  in  the 
belief  that  they  will  render  easier  a  process  not  always  readily 
acquired. 

"  The  tongue  must  be  applied  to  the  roof  of  the  mouth,  so  as 


40  MECHANICAL    DENTISTRY. 

to  interrupt  the  communication  between  the  passage  of  the 
nostrils  and  the  mouth.  The  operator  now  fills  his  mouth  with 
air,  which  is  to  be  passed  through  the  pipe  by  compressing  the 
muscles  of  the  cheeks,  while  he  breathes  through  the  nostrils 
and  uses  the  palate  as  a  valve.  When  the  mouth  becomes 
nearly  empty,  it  is  replenished  by  the  lungs  in  an  instant,  while 
the  tongue  is  momentarily  withdrawn  from  the  roof  of  the 
mouth.  The  stream  of  air  can  be  continued  for  a  long  time 
without  the  least  fatigue  or  injury  to  the  lungs. 

"The  easier  way  for  the  student  to  accustom  himself  to  the 
use  of  the  blowpipe,  is  first  to  learn  to  fill  the  mouth  with  air, 
and  while  the  lips  are  kept  firmly  closed  to  breathe  freely  through 
the  nostrils.  Having  eftected  this  much,  he  may  introduce  the 
mouth-piece  of  the  blowpipe  between  his  lips.  By  inflating  the 
cheeks  and  breathing  through  the  nostrils,  he  will  soon  learn  to 
use  the  instrument  without  the  least  fatigue.  The  air  is  forced 
through  the  tube,  against  the  flame,  by  the  action  of  the  muscles 
of  the  cheeks,  while  he  continues  to  breathe  without  interruption, 
through  the  nostrils.  Having  become  acquainted  with  this 
process,  it  only  requires  some  practice  to  produce  a  steady  jet 
of  flame.  A  defect  in  the  nature  of  the  combustible  used,  as 
bad  oil,  such  as  fish  oil,  or  oil  thickened  by  long  standing  or  by 
dirt,  dirty  cotton  wick,  or  an  untrimmed  one,  or  a  dirty  wick 
holder,  or  a  want  of  steadiness  of  the  hand  that  holds  the  blow- 
pipe, will  prevent  a  steady  jet  of  flame.  But,  frequently,  the 
fault  lies  in  the  orifice  of  the  jet,  as  too  small  a  hole  or  its  partial 
stoppage  by  dirt,  which  will  prevent  a  steady  jet  of  air  and  lead 
to  difficulty.  With  a  good  blowpipe,  the  air  projects  the  entire 
flame,  forming  a  horizontal,  blue  cone  of  flame,  which  converges 
to  a  point  at  about  an  inch  from  the  wick,  with  a  larger,  longer, ' 
and  more  luminous  flame  enveloping  it,  and  terminating  at  a 
point  beyond  that  of  the  blue  flame."  * 

BELLOWS    BLOWPIPE. 

There  are  many  processes  of  the  dental   laboratory  requiring 
the  application  of  a  higher  temperature  than  is  obtainable  with 

*"  The  Practical  Use  of  the  Blowpipe." — Anon. 


GENERATION    AND    APPLICATION    OF    HEAT. 


41 


the  mouth  blowpipe.  A  more  powerful  and  persistent  air 
blast  is  readify  produced  by  a  bellows  or  foot  blower,  used  com- 
monly in  connection  with  a  burner  of  suitable  form  attached  to 
the  common  gas  jet,  by  means  of  which  the  gas  is  furnished 
with  the  oxygen  required  for  its  combustion  in  a  state  of  intimate 
mixture. 

A  simple  and  compact  form  of  bellows  or  foot  blower  is  shown 
in  Fig.  12.  The  pressure  obtainable  with  this  instrument  is 
continuous,  equable,  and  completely  under  the  control  of  the 
operator,  but  the  current  may  be  greatly  increased  in  power 
after  the  rubber  disk  is  distended  until  forced  against  the  net. 

A  bellows  of  similar  construction,  but  with  the  position  of  the 


Fig.  12. 


Fig.  i- 


blower  reversed,  is  shown  in  Fig.  13.  By  this  arrangement  the 
disk  is  less  liable  to  injury,  while  it  prevents  the  valve  from 
picking  up  dirt  from  the  floor. 

A  contrivance  essentially  different  in  its  construction  from  the 
ordinary  bellows  employed  to  produce  the  air  jet  is  shown  in 
Fig.  14,  and  is  known  as  the  "  Burgess  Mechanical  Blowpipe." 
When  in  use,  the  air  is  drawn  into  a  cylinder  and  condensed  in 
an  air  chamber,  ready  to  be  used  in  large  or  small  quantities  at 
the  will  of  the  operator,  by  a  rapid  or  slow  movement  of  the 
treadle.  When  operating,  place  the  entire  foot  upon  the  treadle, 
so  that  an  easy  rocking  motion  is  obtained ;  by  pressing  the  toe 
downward,  air  is  drawn  into  the  cylinder,  and  in  reversing  the 
motion  it  is  driven  into  the  air  chamber  above.     The  pipe  outlet 


42 


MECHANICAL    DENTISTRY. 


is  much  smaller  than  in  the  mouth  blowpipe,  to  enable  a  pres- 
sure to  be  obtained,  which  is  increased  or  diminished  by  a  quick 
or  slow  motion  of  the  treadle.  The  air  chamber  is  easily  filled, 
and  when  so  a  constant  supply  of  pure  air  is  at  the  control  of 
the  operator. 

The  blowpipes  used  in  connection  with  the  bellows  are  of 
various  forms.  Fig.  15  represents  one  form  of  apparatus  employed 
in  the  application  of  the  air  blast  to  the  gas  flame. 

A  movable  gas  jet  attached  to  two  short  arms  of  an  ordinary 


Fig.  14. 


Fig.  15. 


gas  pipe  is  made  to  receive  within  it  the  blowpipe  point  con- 
nected with  the  rubber  tube,  the  air  tube  terminating  a  little 
within  the  open  mouth  of  the  gas  jet ;  it  is  thus  a  tube  within  a 
tube,  with  a  space  between  them  for  the  admission  and  passage 
of  gas.  The  gas,  being  admitted  by  turning  the  tap  connected 
with  the  gas  pipe,  is  ignited,  when  the  current  of  air  from  the 
bellows  will  strike  the  center  of  the  flame  and  project  it  upon 
whatever  is  to  be  heated.  The  connected  portions  of  the  air  and 
gas  jets  are  so  attached  to  the  main  pipe  as  to  admit  of  an  up- 


GENERATION    AND    APPLICATION    OF    HEAT.  43 

ward  and  downward  motion,  while  the  volume  of  gas  and  air  is 
readily  graduated  by  the  stop-cocks  attached  to  the  air  and  gas 
tubes. 

A  bellows  blowpipe,  constructed  on  similar  principles,  but 
admitting  of  greater  latitude  of  movements,  is  exhibited  in  Fig. 
16.  As  will  be  readily  observed,  it  is  capable  of  being  adjusted 
in  any  desired  position.  The  jet  tube  may  be  raised  or  lowered 
to  any  height  and  turned  in  any  direction.  A  touch  will  direct 
the  flame  on  any  point  while  the  blowpipe  stands  in  the  same 
position  on  the  table ;  there  being  no  necessity  for  raising, 
lowering,  or  adjusting  work  before  it. 

Macomber's  gas  blowpipe.  Fig.  17,  differs  somewhat  in  con- 


FlG.  16. 


Fig.  17. 


struction  from  the  latter,  its  capability  of  adjustment  being 
regulated  by  a  ball-and-socket  attachment  which  imparts  to  it, 
at  the  will  of  the  operator,  a  latitude  of  movement  or  adjustment 
of  the  blowpipe  point  that  is  practically  without  limit.  The 
direction  of  the  point,  i,  is  regulated  by  the  joint,  3,  and  the* 
supply  of  gas  controlled  by  the  stop-cock,  2.  The  air  is  sup- 
plied by  the  bellows  through  the  flexible  tube. 

A  very  convenient,  manageable  and  effective  instrument  for 
many  purposes  requiring  the  application  of  heat  in  the  dental 
laboratory  is  the  hand  blowpipe  shown  in  Fig.  18.  It  is  capable 
of  producing  very  high  degrees  of  heat,  but  the  intensity  of  the 
latter  may  be  graduated  at  the  will  of  the  operator,  as  the  stop- 


44 


MECHANICAL    DENTISTRY, 


cocks,  which  arc  both  under  perfect  control  of  the  thumb  of 
the  hand  which  holds  the  blowpipe,  regulate  the  supply  of  gas 
and  control  the  volume  of  air.  The  air  jet  is  one-eighth  inch 
bore,  and  requires  a  supply  from  a  bellows. 

Fig.  19    represents    an    improved    pattern   of    the    Fletcher 

Fig.  18. 


Automaton,  designed  especially  for  crown-  and  bridge-work.  It 
is  made  of  smaller  tubing  than  the  No.  6  A  or  B  Automaton,  the 
end  being  bent  at  an  angle  to  give  greater  facility  in  directing  the 
flame.  The  adjustable  nozzle  is  screwed  on  and  off,  instead  of 
operating  by  a  slip-joint,  as  in  other  patterns  of  the  automaton 
blowpipe.   Its  length  is  increased,  removing  the  hand  farther  from 

Fig.  19. 


the  heat.  The  supply  of  gas  and  air  is  controlled  by  a  longitudinal 
movement  of  the  tube,  instead  of  a  rotative  one.  A  spring  opposes 
the  movement  of  the  hand,  and  a  slight  variation  ofpressure  upon 
the  end-piece,  when  it  is  held  as  shown,  is  sufficient  to  give 
either  a  pointed  jet  or  a  full-sized  brush  flame  at  pleasure.     An 


GENERATION    AND    APPLICATION    OF    HEAT, 


45 


improved  tip  is  used  on  the  air  jet,  and  the  small  blue-pointed 
reducing  flame  is  very  easily  and  perfectly  produced. 

The  gas  passage  does  not  close  entirely,  but  allows  the  pas- 
sage of  enough  gas  to  prevent  the  flame  from  going  out  when 
the  blowpipe  is  not  in  use.  It  can  be  hung  up  by  the  ring  shown 
on  its  body,  when  it  is  desirable  to  get  it  out  of  the  hand. 


Fig.  20. 


Fig.  21. 


Fig.  22. 


Two  very  convenient  forms  ot  the  Fletcher  automatic  blow- 
pipe are  shown  in  Figs.  20  and  21.  The  latter,  which  is  mounted 
on  a  ball  joint,  is  adjustable  at  the  will  of  the  operator. 

In  cases  requiring  a  heat  of  sufficient  intensity  to  readily  fuse 
pure  gold,  as  in  the  construction  of  continuous-gum  work,  where 
this  metal   in  its  unalloyed  form  is  used  to  unite  the  teeth  and 
plate,    the    hot-blast     blowpipe    con- 
trived by  Mr.  Fletcher,  exhibited  in 
Fig.  22,  will  be  found  effixient  for  the 
purpose.     The    air    pipe,   as    will  be 
seen,  is  coiled  around  the  gas  pipe, 
and  both  are  heated  by  three  small 
Bunsen    burners,  the    gas    supply  to 
which  is  regulated  by  a  separate  stop- 
cock, as  shown  in  the    figure.     The 
air  blast  is  obtained  with  the  bellows  or  foot  blower  connected 


46  MECHANICAL    DENTISTRY. 

with  the  blowpipe  by  means  of  a  flexible  rubber  tube.  It  is 
claimed  that  the  heat-producing  power  of  this  simple  device  is 
but  little  inferior  to  that  of  the  oxy-hydrogen  blowpipe,  and 
may  be  useful,  therefore,  in  the  treatment  or  management  of 
highly  refractory  metals  or  substances  not  readily  acted  upon  by 
the  highest  heat  of  the  ordinary  forms  of  bellows  blowpipe. 

The  several  forms  of  bellows  blowpipe  illustrated  in  these 
pages  are  complete  and  efficient,  and  admirably  adapted  to  the 
necessities  of  the  mechanical  operator.  In  most  instances,  the 
jet  may  be  elevated  or  depressed  at  will,  while  the  force  of  the 
air  current  and  the  volume  of  the  gas  flame  can  as  readily  be 
increased  or  diminished.  The  operator  is  thus  enabled,  with  the 
greatest  ease,  to  produce  a  heat  adapted  to  the  most  delicate 
operations,  or  to  instantly  change  it  to  a  heat  so  intense  that 
pure  gold  in  considerable  quantities  is  almost  immediately  fused  in 
the  flame.  They  are,  therefore,  well  adapted  to  all  operations  in 
the  laboratory,  but  will  be  found  of  special  utility  in  the  con- 
struction of  work  requiring  pure  gold  as  a  solder. 

THE    GASOLENE    OR    OXY-CARBON    BLOWPIPE. 

Where  illuminating  gas  is  not  available,  the  oxy-carbon  forge 
or  blowpipe  will  be  found  most  useful.  It  gives  a  high,  steady, 
smokeless,  and  nearly  odorless  blast,  and  at  the  same  time  does 
not  require  either  the  bellows  attachment  or  lung  power.  It  is 
less  expensive  than  gas  or  alcohol,  is  safe,  portable,  durable  and 
is  simple  to  control  and  handle.  It  can  be  changed  instantly 
from  an  intense  heat  to  a  feeble  flame,  or  the  reverse.  The  en- 
tire forge  is  only  about  twelve  inches  high,  having  a  base  nine 
inches  in  diameter,  and  can  be  run  all  day  with  one-half  gallon 
of  74°  deodorized  gasolene  (see  page  62)  without  any  attention, 
excepting  a  few  minutes'  use  with  the  rubber  bulb  to  keep  up 
the  necessary  air  pressure.  This  forge  is  illustrated  in  Figs.  23, 
24,  and  25. 

It  can  be  used  for  vulcanizing,  heating  investments,  soldering, 
melting  metals,  annealing  plates,  for  waxing,  or  any  purpose  for 
which  heat  may  be  required  in  the  laboratory. 


APPLICATION    AND    GENERATION    OF    HEAT. 


47 


Frn.  27. 


Fig.  24. 


48 


MECHANICAL    DENTISTRV. 


OXY-HYDROGEN    BLOWPIPE. 

No  dental  laboratory  appliance  for  heating  purposes  has  ever 
been  devised  that  has  attracted  so  much  attention,  or  elicited 
such  cordial  and  unreserved  praise  by  expert  manipulators,  as 
that  invented  by  Dr.  J.  RoUo  Knapp,  of  New  Orleans,  La.,  and 
shown  in  Fig.  26. 

It  is  described  as  being  to  all  intents  and  purposes  an  oxy- 
hydrogen  blowpipe  divested  of  the  cumbersome  paraphernalia 
usually  accompanying  the  latter,  and  reduced  to  a  practical  size 


Fig.  25. 


and  shape  for  soldering  operations.  It  is  essentially  an  appara- 
tus for  securing  the  consumption  of  hydrogen  in  a  highly  oxy- 
genated atmosphere,  the  resulting  flame  being  second  in  intensity 
only  to  that  of  the  oxy-hydrogen  blowpipe  proper.  It  will  melt 
gold  or  its  alloys  in  quantities  suited  to  its  capacity  almost  in- 
stantly, without  other  exertion  on  the  part  of  the  operator  than 
the  adjustment  of  a  couple  of  small  levers.  It  is  economical  of 
time  and  materials,  and  not  the  least  notable  of  its  good  qualities 
is  its  cleanliness.  Its  inventor  has  been  accustomed  to  do  all  his 
soldering  of  crown-  and  bridge-work  without  leaving  the  operat- 


GENERATION    AND    APPLICATION    OF    HEAT. 


49 


ing  room.  It  can  be  used  wherever  illuminating  gas  is  available. 
Any  of  the  soldering  operations  of  the  laboratory,  from  the 
largest  piece  of  bridge-work  to  the  most  delicate  joining  of  the 
narrowest  bands  or  finest  wires,  are  accomplished  with  equal 
facility.  With  illuminating  gas  of  good  quality  and  sufficient 
pressure,  a  pennyweight  of  twenty-carat  gold  can  be  melted 
in  thirty  seconds.  When  the  investment  is  large,  it  must  first 
be  heated  by  other  means. 

Fig.  26. 


TRin?.^  VtlcU' 


The  apparatus  consists  of  the  blowpipe  attachments,  connected 
to  the  yoke  of  a  nitrous  oxid  gas  cylinder,  the  cylinder  being 
set  upright,  and  secured  by  a  thumb-screw  on  one  end  of  an 
iron  base  or  stand,  at  the  other  end  of  which  is  pivoted  a  table, 
upon  which  to  rest  the  work.  The  blowpipe  proper  is  a  continu- 
ation of  the  outlet  tube  of  the  gas  cylinder.  A  lever-valve,  G, 
regulates  the  supply  of  nitrous  oxid.  Just  beyond  this  valve 
is  the  mixing  chamber  K,  to  which  the  illuminating  gas  is  con- 
ducted from  the  gas  bracket  by  means  of  rubber  tubing,  entering 
4 


50  MECHANICAL    DENTISTRY. 

the  bottom  of  the  chamber  through  the  valved  tube,  C.  The 
lever,  D,  controls  the  supply.  The  mixing  chamber  is  provided 
with  a  gauze  screen  to  prevent  the  flame  from  being  drawn  into 
the  supply  tubes.  Immediately  beyond  the  mixing  chamber  the 
pipe  is  branched  to  afford  two  flames  of  different  sizes,  E  and 
F,  which  can  be  used  independently  of  each  other  or  both  to- 
gether. The  valve-lever,  L,  regulates  the  flame  in  both.  For 
greater  convenience  in  manipulation  the  pipe-nozzles  are  con- 
nected with  the  branched  pipe  by  rubber  tubing.  From  the 
body  of  the  valve  L  an  arm  extends,  at  the  end  of  which  is  a 
small  scalloped  disk  as  a  holder  for  the  flame-nozzles  when  not 
in  use.  In  the  illustration  one  of  the  nozzles  is  shown  in  the 
holder,  the  other  being  directed  to  the  revolving  table. 

SUPPORTS. 

There  are  many  processes  in  the  dental  laboratory  for  which 
it  is  necessary  to  provide  a  suitable  holder  or  support,  as  in 
melting  small  quantities  of  gold  and  silver,  and  in  all  the  varied 
operations  requiring  the  use  of  solder. 

For  melting  or  soldering  small  pieces,  a  variety  of  simple 
devices,  easily  and  economically  constructed,  may  be  used, 
among  which  are  the  following : — 

Charcoal,  either  alone  or  combined  with  other  non-conducting 
substances,  is  very  commonly  employed,  and  being  combustible, 
adds  materially  to  the  heat  of  the  blowpipe  flame.  A  conve- 
nient support  of  this  kind  may  be  made  by  selecting  a  fair-sized 
block  of  compact,  close-grained  charcoal,  derived  from  some  of 
the  hard  woods,  such  as  oak  or  beech,  and  investing  it  in  plaster 
one-half  or  three-fourths  of  an  inch  thick,  one  end  or  side  being 
left  open  and  made  concave,  to  receive  whatever  is  being  heated. 
Or  a  plaster  cup,  two  or  three  inches  deep  and  three  or  four 
inches  in  diameter,  may  be  used,  its  interior  being  filled  with  a 
mixture  of  plaster,  sand,  asbestos,  and  pulverized  charcoal. 
Coke,  encased  in  the  same  manner  as  charcoal,  may  be  substi- 
tuted for  the  latter,  and  has  the  merit  of  being  more  lasting,  but 
in  all  other  respects  is  inferior  for  the  purpose.  Supports  for 
the  uses  under  consideration  are  also  sometimes  made  of  pumice- 
stone. 


GENERATION    AND    APPLICATION    OF    HEAT. 


51 


Prof.  Essig  *  says:  "  Platner's  '  Manual  of  Qualitative  and 
Quantitative  Analysis  with  the  Blowpipe,'  page  15,  gives  a 
method  of  artificially  preparing  good,  solid  supports  of  charcoal 
which  might  be  found  of  value  in  the  dental  laboratory.  It 
consists  of  mixing  charcoal  dust  (which  must  not  be  too  finely 
ground)  with  starch  paste.  The  latter  is  prepared  by  combining 
one  part  of  starch  with  six  parts  of  boiling  water.  These  are 
stirred  in  an  earthen  pot  until  all  the  meal  is  converted  into 
paste.  This  paste  is  rubbed  in  a  porcelain  mortar,  with  frequent 
additions  of  charcoal  dust,  until  the  mass  becomes  too  tough  for 
further  admixture,  when  enough  of  the  coal  dust  is  kneaded  in  by 
the  hands  to  render  the  whole  mass  stiff  and  plastic.  From  this 
the  desired  forms  of  blowpipe  coals  can  be  made,  allowed  to  dry 
gradually  and  thoroughly,  and  then  heated  to  redness  in  a  cov- 


FiG.  27. 


Fig.  28. 


ered  vessel,  so  as  to  char  the  starch  paste.  The  charring  may 
be  regarded  as  complete  when  the  evolution  of  the  gases  from 
the  mass  ceases,  or  when  it  has  been  heated  to  a  dull  redness. 
Coals  thus  formed  are  of  the  proper  firmness,  and  ring  like  ordi- 
nary good  charcoal  when  thrown  on  the  table." 

Manufactured  supports  composed  of  asbestos  and  carbon,  very 
convenient  and  durable,  may  be  obtained  at  the  dental  depots. 
Fig.  27  represents  a  carbon  block  designed  for  melting  and  sol- 
dering, and  Fig.  28  a  carbon  cylinder  used  chiefly  for  soldering 
small  pieces. 

For  soldering  purposes  exclusively,  especially  in  uniting  teeth 
to  a  metallic  base,  either  of  the  following  means  of  support  for 
the  invested  piece  will  be  suitable  :  A  simple  holder,  which  the 


*  "  Dental  Metallurgy." 


52 


MECHANICAL    DENTISTRY, 


operator  himself  can  easily  construct,  may  be  made  of  a  circular 
or  semi-elliptical  piece  of  heavy  sheet  iron,  the  margin  of  which 
is  serrated  and  turned  at  right  angles,  forming  a  cup.  To  the 
under  side  and  center  of  this  an  iron  rod,  ten  or  twelve  inches 
long,  may  be  permanently  riveted,  or  it  may  be  made  to  revolve 
on  the  handle,  so  that  the  heat  may  be  thrown  directly  upon 
any  particular  part  of  the  piece  to  be  soldered  without  disturb- 
ing the  latter. 

A  small  Jumd  furnace  (Fig.  29)  is  sometimes   used,  and  will 
be   found  a  very  convenient   and   useful  apparatus,  not  only  for 


Fig.  29. 


soldering,  but  for  preparatory  heating.  It  consists  of  a  funnel- 
shaped  receptacle  made  of  sheet  iron,  with  a  light  grate  or  per- 
forated plate  of  the  same  material  adjusted  near  the  bottom,  and 
an  opening  on  one  side,  underneath  the  grate,  for  the  admission 
of  air.  The  upper  part  of  the  holder  is  surmounted  by  a  cone- 
shaped  top,  which  may  be  readily  removed  by  a  handle  attached 
to  it,  while  to  the  bottom  of  the  furnace  is  attached  an  iron  rod, 
five  or  six  inches  long  and  terminating  in  a  wooden  handle.  The 
piece  to  be  soldered  is  to  be  placed  inside  on  a  bed  of  charcoal, 
the  top  adjusted  to  its  place, and  the  fuel  ignited;  when  the  case 


GENERATION    AND    APPLICATION    OF    HEAT. 


53 


is  sufficiently  heated,  the  top  may  be  lifted  off,  and  the  piece  re- 
maining in  the  furnace  soldered  with  the  blowpipe  in  the  usual 
manner,  the  furnace  thus  serving  the  purpose  of  a  holder. 

The  Melotte  Clamp  or  Support. — Two  forms  of  a  very  sim- 
ple and  convenient  clamp  or  support,  devised  by  Dr.  George  W. 
Melotte,  of  Ithaca,  N.  Y.,  are  shown  in  Figs.  30  and  31,  and  are 
especially  designed  for  crown-  and  bridge-work. 

It  is  the  design  of  this  invention  to  provide  means  for  holding 

Fig.  .^o. 


gold  crown  collars  and  their  caps  so  that  without  change  of  size 
or  shape  their  closed  joints  can  be  neatly  soldered.  Fig.  30 
exhibits  a  collar,  and  Fig.  31  a  collar  and  cap  thus  held.  A 
slight  pressure  suffices,  and  this  is  effected  by  pushing  the  jaw 
shank  into  the  handle,  which  by  its  spur  is  then  fixed  in  a  piece 
of  charcoal  or  on  the  bench  ;  the  jaws  turn  in  the  handle  to  bring 
the  joint  into  position,  when  the  left  hand  is  set  free  to  manipu- 
late the  solder  while  the  blowpipe  is  directed  by  the  right  hand 


54 


MECHANICAL    DENTISTRY, 


as  usual.  The  cuts  are  two-thirds  size,  and  the  set  consists  of 
Nos.  I  and  2,  the  latter  shown  without  the  handle,  which  will 
grip  either  shank. 

FURNACES. 

It  would  be  inconsistent  with  the  design  of  the  present  work 
to  introduce  a  description  of  any  form  of  furnace  other  than 
those  of  practical  use  to  the  dentist.  Many  of  those  used  in  the 
arts,   or  for   chemical   and    pharmaceutical    purposes,   embrace 

Fig.  32. 


almost  endless  varieties,  and  have  no  special  adaptation  to  the 
uses  required  of  them  in  the  dental  laboratory. 

Draft  or  Wind  Furnace. — A  very  convenient,  portable, 
and  economical  furnace  may  be  made  of  sheet  iron,  of  any 
desired  shape  or  dimensions,  though  usually  of  small  size  and 
cylindrical  in  form.  A  light  grate,  or  heavy  piece  of  sheet  iron, 
perforated  with  holes,  to  admit  of  the  passage  of  air,  should  be 
adjusted   near  the  bottom,  while  above  and  below  the  grate  are 


GENERATION    AND    APPLICATION    OF    HEAT. 


55 


two  openings,  the  lower  one  communicating  with  the  ash  pit, 
and  the  upper  one  for  the  introduction  of  fuel  and  substances 
to  be  heated.  By  surmounting  this  simple  apparatus  with  a 
pipe,  or  connecting  it  with  the  Hue  of  a  chimney,  it  will  be  found 
efficient  in  many  of  the  minor  operations  of  the  shop,  as  melting 
metals,  heating  pieces  preparatory  to  soldering,  annealing,  etc. 

A  more  durable  and  serviceable  draft  furnace,  however,  may 
be  built  of  masonry,   a    convenient    form    of  which    is    repre- 

FiG.  33. 


sented  in  Fig.  32.  The  construction  of  this  stationary  fixture 
is  so  plainly  exhibited  in  the  cut  that  any  extended  description 
of  it  is  deemed  unnecessary.  The  upper  holes  represent  the 
entrance  to  the  fire  chambers,  which  are  distinct  from  each 
other  ;  the  lower  ones  communicate  with  the  ash  pit,  which  is 
common  to  both  chambers.  Two  fire  apartments  are  here  shown, 
one  for  melting  and  refining  the  more  precious  metals,  heating 
up  for  soldering,  etc.,  the  other  being  used  exclusively  for 
fusing  the  baser  metals,  as    zinc,  antimony,  lead,  etc.      These 


56      ■  MECHANICAL    DENTISTRY. 

furnaces  are  sometimes  constructed  with  a  single  fire  chamber, 
but  the  one  exhibited  is  in  every  way  preferable. 

Baking  Furnace. — The  chief  purposes  to  which  these  fur- 
naces are  applied  are  the  manufacture  of  porcelain  teeth,  single 
and  in  sectional  blocks,  the  preparation  of  silicious  compounds, 
and  the  construction  of  what  is  known  as  "  continuous-gum 
work."  One  of  the  most  approved  forms  of  this  furnace  is 
exhibited  in  Fig.  33. 

The  body  of  the  furnace  rests  upon  a  cast-iron  framework  or 
basement,  which  serves  the  purpose  of  an  ash  pit.  The  grate 
immediately  over  this  inclines  from  each  side  of  the  furnace 
toward  the  bottom  and  the  center  of  the  ash  pit,  to  afford  mxore 
ample  room  for  fuel  directly  underneath  the  lower  muffle.  The 
upper  portion  or  body  of  the  furnace  is  made  of  fire  clay,  and 
contains  three  mtiffles  arranged  horizontally;  the  upper  two, 
termed  "  annealing  muffles,"  are  designed  more  especially  for 
drying  substances,  partial  heating  preparatory  to  final  baking, 
and  to  receive  substances  from  the  lower  muffle  to  be  gradually 
cooled.  The  lower  or  main  muffle  is  for  general  baking  purposes 
requiring  the  employment  of  extreme  degrees  of  heat.  Each 
muffle  is  provided  with  fire-clay  slabs  or  slides,  on  which  sub- 
stances to  be  heated  are  placed  and  introduced  into  the  muffles; 
and  also  plugs  of  the  same  material  to  close  the  openings  to  the 
former.  Openings  are  made  on  each  side  of  the  furnace,  inter- 
mediate between  the  muffles,  for  the  introduction  of  fuel,  and  to 
afford  ready  access  to  the  latter  with  tongs  or  other  implements. 
These  entrances  are  also  provided  with  plugs,  which  are  applied 
during  the  process  of  heating.  This  furnace  should  be  con- 
nected with  a  flue  having  a  strong  and  unobstructed  draft. 

The  Tees  Furnace. — A  furnace  of  somewhat  similar  con- 
struction, devised  by  Dr.  Ambler  Tees,  is  shown  in  Fig.  34.  Dr. 
Tees,  in  a  communication  to  the  author,  says  concerning  this 
appliance,  which  he  designates  as  the  "  Lilliput "  furnace  :  "  Con- 
tinuous-gum work  has  heretofore  been  looked  upon  as  formid- 
able, on  account  of  the  necessity  of  using  large  furnaces  to 
obtain  the  requisite  degree  of  heat ;  but  since  the  introduction 
of  the  Lilliput  furnace,  in  1880,  and  the  systematic  way  of  man- 
aging it,  it  has  become  a  pleasure  instead  of  a  terror." 


GENERATION    AND    APPLICATION    OF    HEAT.  57 

This  little  furnace  is  made  of  fire-clay;  it  is  but  i^j/i  inches 
high,   12   inches   wide,  and   8   inches   deep,  with   walls    i    inch 

Fig.  34. 


thick ;  being  divided  into  three  sections,  it  can  be  handled  and 
managed  by  a  child.  Scarcely  more  than  half  a  peck  of  coke  is 
necessary  for  each  heat.     In  the  fall,  winter,  and  spring,  when 


58 


MECHANICAL    DENTISTRY. 


Fig.  35. 


the  draft  is  at  its  best,  a  coat  of  body  can  be  fused  in  about 
thirty-five  minutes  after  the  fire  is  lighted,  and  in  the  summer 
within  fifty  minutes.  By  having  the  coke  properly  screened, 
and  the  kindling  wood  dry,  and  a  convenient  receptacle  for  them, 
the  labor  of  starting  the  fire  is  scarcely  more  than  lighting  the 
gas.  It  is  for  sale,  with  all  the  necessary  appurtenances,  by 
dental  dealers. 

A  modification  of  the  last-named  furnaces,  more  recently 
and  especially  designed  and  introduced  for  continuous-gum 
work,  is  exhibited  in  Fig.  35.  The  fire  pit 
below  the  mufifle  is  of  more  than  usual 
capacity,  insuring,  it  is  claimed,  perfect 
results  at  each  baking.  The  part  which  is 
subjected  to  the  greatest  heat  is  free  from 
angles  and  incased  with  sheet  iron,  render- 
ing it  less  liable  to  crack  from  long  use. 
The  fire  or  ashes  may  be  withdrawn  by 
removing  the  two  projecting  grate  bars.  It 
is  24  inches  high  and  12^  inches  in  diam- 
eter. 

As  the  purposes,  heretofore  stated,  for 
which  these  several  furnaces  are  designed 
require  a  steady,  intense  and  persistent 
heat,  the  fuels  commonly  used,  as  fulfilling 
most  perfectly  these  indications,  are  coke, 
or  a  mixture  of  charcoal  and  coke,  and  anthracite,  preference 
being  given,  by  many,  to  the  latter. 

It  will  be  observed  that,  in  connection  with  the  several  kinds 
of  furnaces  heretofore  mentioned,  heat  is  generated  by  the  use 
of  solid  fuels.  Within  the  past  few  years,  baking  or  muffle  fur- 
naces have  been  constructed  with  reference  to  their  special 
adaptability  to  the  use  of  gas  in  combination  with  the  air  blast. 
While  these  later  devices  commend  themselves  on  the  score  of 
their  greater  convenience  and  economy  of  time  in  firing,  and 
their  freedom  from  the  dirt  and  smoke  attending  the  use  of  solid 
fuels,  their  successful  application  to  the  special  uses  for  which 
they  are  mainly  designed,  has  been  attended  with  difificulties 
which  have  heretofore  been  adverse  to  their  general  adoption  by 


GENERATION    AND    APPLICATION    OF    HEAT.  59 

the  profession,  and  which  it  has  been  the  aim  of  inventors  to 
overcome.  This  has  been  measurably,  if  not  entirely,  accom- 
plished, and  the  successes  so  far  attained  give  fair  promise  of  a 
complete  revolution,  at  no  distant  day,  in  the  modes  of  applying 
heat  in  all  operations  concerned  in  the  fabrication  of  the  various 
forms  of  dental  porcelain.  Perhaps  the  chief  obstacle  to  the 
successful  use  of  gas  in  connection  with  the  air  blast  in  the  pro- 
cesses relating  to  the  manufacture  of  porcelain  teeth,  gum 
enamels,  continuous-gum  work,  etc.,  is  in  the  increased  liability 
to  so-called  "  gasing,"  or  the  formation  of  bubbles,  due  to 
absorption  and  elimination  of  gas  that  finds  its  way  into  the 
muffle  during  the  process  of  baking.  The  manner  in  which  this 
accident  occurs  is  thus  accounted  for  in  a  communication  to  the 
author  from  Dr.  C.  H.  Land,  of  Detroit,  Michigan.  Alluding  to 
the  kind  of  furnaces  under  consideration,  the  writer  says  : — 

"  To  be  able  to  fuse  the  body  and  enamel  of  which  artificial 
teeth  are  composed  in  an  easy  and  convenient  manner  is  a  thing 
the  profession  have  studiously  sought  after,  realizing  that,  when 
properly  accomplished,  the  means  to  elevate  prosthetic  dentistry 
from  an  ordinary  mechanical  enterprise  to  one  of  true  art,  would 
be  at  hand.  The  mere  construction  of  a  furnace  after  the  usual 
modes  has  been  simple  enough,  and  the  question  of  securing 
the  necessary  degree  of  heat  was  long  ago  accomplished.  How- 
ever, the  ideal  furnace  demanded  much  more.  It  must  possess 
not  only  the  capacity  of  a  coal  or  coke  fire,  but  also  accomplish 
the  work  in  less  time,  and  require  but  the  minimum  amount  of 
exertion  to  operate  it.  Of  the  many  attempts  to  produce  such, 
nearly  all  have  failed,  owing  to  technicalities  that  were  not  well 
understood. 

"  After  many  experiments,  and  their  accompanying  failures,  it 
has  been  demonstrated  that  to  heat  an  eight-inch  muffle,  three 
and  one-half  by  two  and  one-half  inches  in  diameter,  to  over 
2800°  F.,  represents  about  a  one-man  power  equivalent  to  the 
exertion  of  running  the  ordinary  foot  lathe  or  the  No.  9  bellows, 
as  manufactured  by  the  Buffalo  Dental  Manufacturing  Company, 
which  gives  a  working  pressure  of  one  and  one-half  pounds  to 
the  square  inch,  and  corresponds  exactly  to  the  required  amount 
of  air  pressure  and  volume  necessary  to  heat   an    eight-inch 


6o 


MECHANICAL    DENTISTRY. 


muffle  to  2800°  F.  Therefore,  to  make  a  furnace  larger  would 
require  too  much  power,  and  one  smaller  would  not  do  for  large 
pieces  of  work.  In  the  production  of  a  suitable  furnace,  the 
whole  working  apparatus  must  be  as  nearly  air-tight  as  possible, 
the  supply  of  gas  and  air  must  be  easily  controlled  and  well 
balanced,  with  the  least  amount  of  friction  in  the  passage  through 
the  pipes.  These,  with  many  minor  details,  form  the  basis  of  a 
practical  gas  furnace. 


CASING    THE    BODY    AND    ENAMEL. 

"  The  most  serious  trouble  with  all  gas  furnaces  has  been  the 
extreme  liability  of  injuring  the  body  and  enamel  by  what  has 
been  commonly  called  '  gasing.'  The  accompanying  illustration, 
Fig.  36,  will  make  the  philosophy  of  combustion  more  clear,  and 
give    the    reasons    why  teeth    are   injured.     A   represents    the 

burner;  B  B  B,  fire-brick 
lining;  C  C  C,  combustion 
chamber;  D,  interior  of  muf- 
fle. The  arrows  indicate  the 
direction  of  the  blast.  The 
space  in  the  combustion  cham- 
ber between  the  lines  E  E 
is  where  carbon  monoxid  is 
formed,  a  gas  containing  one 
equivalent  less  of  oxygen  than 
carbon  dioxid,  simply  an  im- 
perfect state  of  combustion. 
It  is  this  gas  that  injures  the 
body  and  enamel.  By  refer- 
ence to  the  illustration,  it  will 
be  seen  that  the  little  arrows 
are  made  to  appear  passing 
through  the  pores  of  the 
muffle,  and  as  the  direction 
of  the  blast  from  the  burner 
A  is  directly  against  the  bottom  of  the  muffle,  with  a  pressure 
of  one  pound  to  the  square  inch,  a  portion  of  the  carbon  mon- 
oxid is  extremely  liable  to  be  forced  through  its  pores,  and  will 


GENERATION    AND    APPLICATION    OF    HEAT.  6 1 

be  taken  up  with  the  body  during  the  first  and  second  biscuiting, 
here  to  remain  until  the  enameling  process,  and  as  this  takes  a 
much  higher  degree  of  heat,  it  causes  the  gas  to  be  eliminated, 
as  shown  in  the  numerous  small  bubbles  on  the  surface.  The 
space  between  the  lines  E  E,  and  within  the  combustion  chamber 
C  C  C,  should  be  known  as  the  first  stage  of  combustion,  where 
a  certain  portion  of  carbon  monoxid  is  always  present,  and  the 
space  above  the  line  F,  within  the  chamber  C,  should  be  known 
as  the  second  stage,  which  is  perfect  combustion.  In  the  first 
stage  of  combustion  one  equivalent  of  oxygen  from  the  atmos- 
phere unites  with  the  hydrocarbon  to  form  carbon  monoxid  ;  in 
the  second  stage,  two,  or  perhaps  three,  unite  to  form  carbon 
dioxid,  or  carbonic  acid.  Perfect  combustion  is  always  at  the 
extreme  point  of  the  blowpipe,  as  shown  in  the  illustration. 

"  The  attempt,  therefore,  should  be  to  place  the  muffle  as 
nearly  as  possible  in  the  center  of  perfect  combustion.  As  car- 
bon monoxid  is  not  consumed  short  of  a  temperature  of  over 
2200°  F.,  the  teeth  should  be  kept  in  front  of  the  muffle  until  it 
approaches  a  white  heat.  Starting  from  a  cold  muffle  this  will 
take  about  twelve  minutes,  and  they  should  be  gradually  carried 
to  the  extreme  end.  At  a  high  temperature,  there  is  very  little 
danger  of  gasing,  unless  a  greater  quantity  of  gas  is  supplied 
than  the  furnace  is  capable  of  burning.  Having  constructed  a 
furnace,  and  being  familiar  with  many  other  details  that  provided 
a  means  to  overcome  all  the  apparent  difficulties,  the  success  of 
properly  baking  teeth  seemed  to  be  assured,  until  the  muffle 
began  to  crack,  which  usually  started  in  the  second  or  third 
enameling  heat.  This  let  in  such  a  quantity  of  monoxid  of  car- 
bon as  to  ruin  the  teeth.  Here  was  a  difficulty  that  was  overcome 
by  forcing  a  quantity  of  superheated  air  into  the  muffle,  and 
backing  all  foul  gases  out.  This  proved  to  be  a  cure  for  gasing, 
but  added  an  excess  of  oxygen,  and  it  was  found  that  this  had  a 
tendency  to  bleach  the  gum  enamel  to  a  lighter  shade.  The 
next  siep  was  to  inject  a  pure  atmosphere  of  nitrogen  into  the 
muffle,  it  being  a  neutral  gas,  not  uniting  radically  with  any- 
thing. This  was  eminently  successful,  and  thoroughly  demon- 
strated the  fact  that  porcelain  baked  in  an  atmosphere  of  nitro- 
gen was  absolutely  perfect,  both  in  color  and  texture.    It  therefore 


62  MECHANICAL    DENTISTRY. 

gives  me  pleasure  to  be  able  to  announce  to  the  profession  that  the 
baking  of  all  kinds  of  porcelain  with  any  of  the  hydrocarbons 
has  been  brought  within  the  range  of  every  dental  practitioner, 
so  that,  with  a  little  experience  and  knowledge  of  the  above 
facts,  artificial  teeth  can  be  baked,  with  unerring  precision,  in  a 
very  comfortable,  cheap  and  easy  manner.  By  a  simple  attach- 
ment, each  furnace  produces  its  own  nitrogen  as  fast  as  needed, 
and  with  recent  improvements  in  the  construction  of  muffles, 
and  the  aid  of  a  small  motor,  the  author  has  been  able  to 
maintain  a  constant  and  uniform  temperature  above  2800°  F., 
by  which  a  slab  of  sectional  gum  teeth  was  completed  every 
seven  minutes,  at  the  will  of  the  operator. 

OLEFIANT    GAS    AND    GASOLENE. 

"  defiant  gas,  with  which  nearly  all  our  cities  and  towns  are 
supplied,  is  a  compound  of  h\'drogen  and  carbon.  Its  symbols 
are  C2H4,  differing  from  gasolene  only  in  its  specific  gravity,  the 
composition  of  the  latter  being  also  C,2H4.  The  former  will 
rise  to  the  top  of  a  building,  while  the  latter  will  fall.  The 
former  is  more  penetrating,  therefore  more  liable  to  gas  the 
teeth,  and  hence  requires  more  care  in  handling.  The  quality 
varies  in  different  localities,  and  sometimes,  owing  to  the  pres- 
ence of  ammonia,  it  may  injure  the  teeth,  or  it  may  be  too  thin. 
When  properly  purified,  it  should  be  a  rich  hydrocarbon.  The 
uncertainty  of  its  qualities  is  frequently  the  cause  of  failure.  To 
be  successful  with  gas  furnaces,  it  is  absolutely  necessary  to 
have  a  pure  and  rich  hydrocarbon.  When  the  gas  pressure  is 
weak  or  the  quality  is  poor,  a  gasolene  generator  may  be  attached 
to  the  pipe  and  the  current  allowed  to  pass  through.  This 
takes  up  a  large  percentage  of  the  gasolene  and  provides  a  very 
rich  quality  of  gas.  The  eighty-seven  per  cent,  is  the  best ; 
seventy-four  per  cent,  is  too  heavy  to  use  without  requiring  heat 
to  vaporize  it.  By  applying  to  the  Combination  Gas  Machine 
Company  a  supply  can  be  had.  When  pure  gasolene  is  used,  it 
is  necessary  to  have  a  generator  so  arranged  that  a  portion  of 
the  air  from  the  bellows  will  pass  through  it.  This  carries  the 
vapor  into  the  furnace,  where  it  becomes  mixed  with  the  proper 
quantity  of  air,  and  will  produce  as  good,  if  not  better,  results 


GENERATION    AND    APPLICATION    OF    HEAT.  63 

than  any  other  hydrocarbon.  All  kinds  of  crucible  and  muffle 
work  can  be  done  equally  well,  also  soldering  and  brazing  with 
the  blowpipe.  One  gallon  of  gasolene  costs  fifteen  to  twenty 
cents  ;  this  will  bake  one  set  of  teeth.  Therefore  it  will  be  seen 
that  dentists  living  in  localities  where  there  is  no  gas  will  not  be 
deprived  of  practically  the  same  advantages  as  their  city 
brethren." 

The  Land  Furnace. — The  following  is  a  description  of  a  fur- 
nace, invented  by  Dr.  Land,  designed  especially  to  overcome  the 
trouble  spoken  of  above,  as  well  as  to  provide  other  advantages  : — 

Size  No.  I  is  especially  adapted  for  all  kinds  of  muffle  work, 
crucible  work,  blowpipe  work,  forging  and  brazing,  assaying,  and 
small  castings  of  iron,  brass  and  steel.  A  muffle  8  inches  long, 
3^  inches  wide,  2^  inches  high,  inside  measurement,  can  be 
heated  to  over  3240°  F.  in  twenty-five  minutes,  sufficient  to 
melt  wrought  iron.  Fig.  37  represents  the  furnace  closed  and 
ready  for  muffle  work.  A  A  is  an  iron  pipe,  capable  of  both  a 
sliding  and  a  swinging  motion  (see  L,  Fig.  38),  to  which  the 
door  or  plug  is  securely  attached.  There  is  a  small  hole  in  the 
door,  covered  with  a  piece  of  mica,  through  which  all  operations 
can  be  seen.  Observe  that  the  iron  pipe  is  connected  with  rub- 
ber tubing,  B,  and  with  pipe  having  an  air  cock,  C,  which  regu- 
lates the  quantity  of  air  passing  into  the  mouth  of  the  muffle. 
It  will  also  be  noticed  that  the  pipe  passes  over  the  two  holes, 
D  D  ;  thus  by  the  escaping  flame  the  pipe  is  heated  to  redness 
and  provides  a  superheated  air  before  reaching  the  muffle  ;  this 
column  of  air  forced  into  the  muffle  keeps  up  a  counter  pressure 
within,  so  much  greater  than  the  pressure  produced  by  the  blast 
within  the  fire  chamber  that  all  foul  gases  are  prevented  from 
entering  the  muffle  even  though  it  is  cracked  ;  thus  the  most 
delicate  porcelain  can  be  baked  without  the  least  danger  of 
so-called  gasing.  Also,  it  will  be  seen  that  by  connecting  the 
rubber  pipe  with  retorts  of  gasometers  any  desired  vapor  or  gas 
could  be  forced  into  the  muffle,  making  the  furnace  invaluable 
for  scientific  experiments. 

Fig.  38  illustrates  the  furnace  thrown  open,  being  swung  on 
hinges  at  the  back,  exposing  the  muffle,  E.  The  groove,  P  P,  is 
packed  with  asbestos  fiber,  so  that  when  the  sections  are  brought 


64 


MECHANICAL    DENTISTRY. 


together  the  furnace  will  be  perfectly  air  and  gas  tight.  The 
hooks,  F  F,  are  to  hold  the  upper  section  secure  to  the  lower. 
The  gas  and  air  connections  are  so  arranged  that  the  ordinary 
blowpipe  can  be  attached,  as  shown  at  G.     When  the  muffle,  E, 


Fig.  37. 


is  removed,  it  exposes  two  burners  and  a  fire-brick  surface  made 
to  fit  the  various  appliances  for  crucible,  ladle,  and  blowpipe 
work.  One  or  both  burners  can  be  operated  in  conjunction  with 
the  blowpipe,  G.  The  air  cock,  R,  is  to  provide  a  means  for 
shutting  off  the   air  supply  from  either    burner  when  required. 


GENERATION    AND    APPLICATION    OF    HEAT. 


65 


H  is  the  gas  supply ;  K,  air  pipe  connecting  with  the  bellows. 
Size  of  muffle,  inside  measurement,  8  inches  long,  3^  inches 
wide,  2^^  inches  high.  With  gasolene  gas  porcelain  teeth  can 
be    enameled  in  from  10  to  15  minutes;  with  ordinary  city  gas 

Fig.  38. 


in  from  15  to  25  minutes,  according  to  quality.  In  30  minutes 
a  heat  sufficient  to  destroy  the  muffle  can  be  produced,  which 
indicates  a  temperature  of  over  3240°  F.,  much  higher  than  is 
ever  needed  for  any  kind  of  work,  except  the  fusing  of  platinum. 
5 


66 


MECHANICAL    DENTISTRY. 


Three-eighths  inch  gas  pipe  will  supply  sufficient  gas  and  can  be 
worked  with  ordinary  foot  bellows. 

The  Rollins  Furnace. — A  gas  muffle  furnace,  with  hot-air 
blast  attachment,  invented  by  Dr.  William  Herbert  Rollins,  of 
Boston,  Mass.,  is  exhibited  in  Figs.  39  and  40.  This  furnace, 
designed  especially  for  firing  dental  enamels  and  porcelains  and 
for  continuous-gum  work,  has  been  used  successfully  by  the 
inventor  for  several  years,  and  ranks  among  the  best  of  its  kind 
for  the  purposes  indicated.  The  following  abstract,  taken  from 
a  paper  read  before  the  Society  for  the  Advancement  of  Oral 
Science  and  subsequently  published,  with  illustrations,  in  the 
"  Items  of  Interest,"  is  descriptive  of  the  appliance  under  con- 
sideration : — 

Fig.  39.  Fig.  40. 


"  The  furnace  shown  in  Figs.  39  and  40  will  give  a  heat  from  a 
dull  red  to  a  light  so  bright  that  an  object  in  the  muffle  is  invisi- 
ble. Looking  at  the  figures  will  enable  any  dentist,  by  means 
of  the  following  brief  description,  to  make  a  similar  one  :  The 
furnace  consists  of  a  cylinder  of  sheet  iron  ten  inches  in  diameter 
and  eleven  inches  high.  It  has  a  handle  and  an  iron  door.  The 
cover  is  a  similar  cylinder,  two  inches  deep.  Both  are  lined 
with  porous  fire-clay,  two  inches  thick.  The  furnace  walls  have 
four  holes  in  them.  Three  of  these  holes  give  passage  to  three 
tuyeres,  the  fourth  is  for  a  No.  3  muffle,  the  mouth  of  which  is 
closed  by  an  iron  door  lined  with  asbestos.  The  door  is  per- 
forated by  a  platinum  tube,  through  which  passes  the  platinum 
trial  rod,  with  a  small  spoon  end  for  the  test  piece.     This  rod 


GENERATION    AND    APPLICATION    OF    HEAT.  6/ 

can  be  withdrawn  from  time  to  time,  to  look  at  the  test  piece. 
At  the  front  of  the  furnace  are  two  iron  tubes,  one  for  gas,  the 
other  for  air.  These  pass  under  the  fire-clay  arch,  where  they 
are  brought  to  a  yellow^  heat  by  the  waste  gases  as  they  escape 
through  the  slit  in  the  top  of  the  furnace.  (See  Fig.  40.)  Each 
of  these  tubes  divide  into  three  branches  at  the  back  of  the  fur- 
nace, where  the  gas  tubes  enter  the  air  tubes.  In  this  way  three 
double  tuyeres  are  made,  their  mouths  corresponding  to  the 
holes  in  the  furnace.  This  arrangement  is  necessary,  for  if  the 
heated  air  and  gas  are  allowed  to  mix  before  reaching  the 
mouths  of  the  tuyeres  these  would  be  destroyed  by  the  intense 
heat.  Fig.  40  is  a  perpendicular  section  of  the  furnace.  The 
course  of  the  heated  gases  is  indicated  by  the  arrows." 

As  matter  having  intimate  relation  to  the  baking  of  dental 
porcelain  by  the  means  described  and  illustrated  in  these  pages, 
the  following  observations  of  Dr.  Rollins,  in  discussing  the 
causes  of  "  gasing  "  in  firing  mineral  teeth,  in  addition  to  those 
offered  by  Dr.  Land  on  the  same  subject,  will  not  be  without 
interest  to  those  having  the  management  of  furnaces  used  for 
ceramic  processes  in  the  "dental  laboratory.     He  says  : — 

"  In  my  first  experiments  for  making  enamels  for  filling  conspic- 
uous cavities  in  teeth,  difficulty  was  sometimes  found  in  making 
the  enamel  base  of  a  pure  translucent  white.  As  the  result  of 
somewhat  elaborate  tests,  it  was  found  that  the  gray  or  green 
tint  was  due  to  the  reduction  of  some  of  the  lead  oxid.  A 
similar  difficulty  was  encountered  when  the  enamel  base  was 
fritted  with  the  metallic  oxids  necessary  to  give  it  the  shade  of 
the  teeth.     Here  the  oxids  themselves  were  reduced. 

"  It,  therefore,  seemed  probable  that  the  so-called  gasing  in 
mineral  teeth  came  from  a  similar  cause. 

"  Many  experiments  and  analyses  were  made  to  test  the  mat- 
ter, and  though  it  is  not  worth  while  to  give  these  in  detail,  one 
experiment,  which  is  easily  tried,  will  be  mentioned  :  After  having 
made  a  furnace  like  the  one  described,  light  the  gas  and  open  the 
air  valve.  When  the  heat  is  high  enough,  put  an  unbaked  tooth 
into  the  muffle.  When  taken  out  the  color  will  be  pure.  Now 
diminish  the  oxygen  by  partly  closing  the  air  valve.  Put  in  an- 
other unbaked  tooth.     When  this  is  removed  it  will  be  found 


68 


MECHANICAL    DENTISTRY. 


Fig.  41. 


gased.  The  same  result  will  follow  with  the  air  valve  in  the 
same  position  as  in  the  first  experiment,  if  the  supply  of  gas  is 
increased.  In  experiments  with  dental  enamels  and  porcelain, 
it  is  advisable  to  have  a  slight  excess  of  air  in  the  furnace. 
Where  the  color  used,  as,  for  example,  platinum,  yields  the 
proper  tint  in  the  metallic  state,  this  precaution  is  unnecessary, 
as  in  these  cases  the  color  has  no  oxygen  to  give  up." 

The  Ferrier's  Furnace,  Fig.  41,  is  a  compact  and  convenient 
heater  designed  especially  for  continuous-gum  work ;  it  is  opera- 
ted with  gas  and  the  air  blast  of  an  ordinary  foot  blower.  By  this 
means  a  heat  is  generated  sufficient  to  fuse  gum  body  and  enamel 
in  a  much  shorter  time  than  when  solid  fuel  is  used  in  connection 
with  coke  or  anthracite  furnaces.  In  commendation  of  this  fur- 
nace, the  inventor  says  :  "  This  furnace, 
combining  cleanliness,  utility,  simplicity, 
certainty,  economy  and  durability,  which 
is  the  outcome  of  years  of  experiments, 
has  been  brought  to  the  minimum  of 
difficulty  with  the  maximum  for  work- 
ing, for,  although  only  six  inches  cube, 
sufficient  heat  can  be  produced  in  from 
five  to  ten  minutes  to  fuse  the  gum  body 
or  enamel  for  continuous-gum  facings 
(or  work)  for  mounting  on  vulcanite,  cel- 
luloid, or  gold." 

Gas  Crucible  Furnace  Without 
Blast. — Fig.  42  represents  a  small  cru- 
cible furnace  that  will  be  found  very 
convenient  for  melting  and  refining  the 
precious  and  more  infusible  metals  em- 
ployed by  the  dentist.  It  takes  cruci- 
bles up  to  23^2  by  2yl  inches  outside, 
and  with  a  three-foot  chimney  will  melt  copper,  gold,  silver,  etc., 
in  about  ten  minutes,  or  cast  iron  in  thirty  minutes  from  the  time 
the  gas  is  lighted. 

The  construction  of  the  burner  used  with  this  furnace  is  illus- 
trated by  the  sectional  diagram,  Fig.  43,  and  is  thus  described: 
''  The  gas  enters  a  chamber  at  the  bottom  of  the  burner,  through 


GENERATION    AND    APP.LICATION    OF    HEAT. 


69 


a  device  similar  to  a  Bunsen  burner,  mixing  with  air  as  it  enters, 
and  is  burned  at  the  upper  ends  of  a  series  of  concentric  tubes, 
furnishing  air  spaces  alternately  with  those  supplying  the  mix- 
ture of  gas  and  air.  The  whole  burner  is  constructed  of  iron, 
and  will  be  found  better  able  to  withstand  an  intense  heat,  more 
durable  and  quicker  in  its  operation,  than  the  old  pattern  with 
gun-metal  tubes.  In  case  metal  should  be  spilled  into  the 
burner,  it  can  be  easily  taken  apart  for  its  removal. 


Fig.  42. 


Fig.  43. 


"  Each  part  of  the  burner  is  lettered,  and  in  case  of  accident 
it  can  be  supplied  at  a  small  expense  by  specifying  the  letter  on 
the  piece  desired. 

"The  burner  in  its  present  shape  is  believed  to  be  the  most 
efficient  and  economical  yet  devised  for  furnace  purposes." 

The  following  instructions  in  the  use  of  this  furnace  should 
be  observed  : — 

"  A  chimney  or  stove  pipe,  eight  or  ten  feet  high,  may  be 
used  as  a  fixture,  and  the  draught   partially  stopped  with   a 


70 


MECHANICAL    DENTISTRY. 


damper  or  slide  when  lower  temperatures  are  required,  the  gas 
being  turned  down  in  proportion  ;  the  guide  for  the  proper  adjust- 
ment being  that  under  all  circumstances  the  flame  must 
JUST  COVER  the  CRUCIBLE  OR  MUFFLE,  but  uot  extend  into  tlie 
chimney  so  as  to  make  it  red  hot.  When  the  flame  covers  the 
crucible  or  muffle  the  gas  is  doing  its  extreme  duty  under  the 
most  favorable  circumstances,  without  waste.  Particles  of  flux 
should  not  be  allowed  to  fall  on  the  fire-clay  casing,  where  the 
parts  touch  each  other;  and  the  power  of  the  furnace  should 
not  be  urged  too  far  by  the  use  of  very  long  chimneys,  as  there 
is  danger  of  the  fusion  of  the  fire-clay  parts  together,  so  that 
they  cannot  be  separated.  Fire-clay  fittings,  as  a  rule,  cannot 
be  safely  used  for  temperatures  much  exceeding  the  fusing  point 

Fig.  44. 


of  cast  iron.  Plumbago  fittings  and  crucibles  must  be  Jieated 
sloivly  the  first  time  they  are  7csed.  After  the  first  time  they  may 
be  subjected  instantly  to  the  full  power  of  the  furnace  without 
injury." 

Gas  Crucible  Furnaces  with  Blast. — A  small,  compact, 
and  convenient  crucible  furnace  is  shown  in  Fig.  44.  Of  this 
simple  but  powerful  heating  apparatus,  which  will  be  found 
especially  adapted  to  the  necessities  of  the  dental  laboratory, 
the  manufacturers  *  observe: — 

"  Owing  to  the  discovery,  by  Mr.  Fletcher,  of  a  singularly 
perfect  non-conducting  furnace  casing,  we  are  enabled  to  pro- 
duce the  first  really  simple  gas  furnace  ever  constructed.     This 


*  Buffalo  Dental  Manufacturing  Company. 


■GENERATION    AND    APPLICATION    OF    HEAT.  J I 

material  is  onh^  about  one-sixth  the  weight  of  fire-clay,  and  has 
not  one-tenth  its  conducting  power  for  heat. 

"The  furnace  consists  of  a  simple  pot — for  holding  the  cruci- 
ble— with  a  lid  and  a  blowpipe,  all  mounted  on  a  suitable  cast- 
iron  base.  As  compared  with  the  ordinary  gas  furnace  it  appears 
almost  a  toy,  owing  to  its  great  simplicity. 

"  The  casing  holds  the  heat  so  perfectly  that  the  most  refrac- 
tory substances  can  be  fused  with  ease,  using  a  common  foot 
blower.  Haifa  pound  of  cast  iron  requires  from  7  to  12  minutes 
for  perfect  fusion,  the  time  depending  on  the  gas  supply  and 
pressure  of  air  from  the  blower. 

"  The  power  which  can  be  obtained  is  far  beyond  what  is 
required  for  most  purposes,  and  is  limited  only  by  the  fusibility 
of  the  crucible  and  casing. 

"  The  crucible  will  hold  about  ten  ounces  of  gold. 

"  An  ordinary  gas  supply  pipe,  -f^  or  -|,  will  work  it  efficiently. 
It  requires  a  much  smaller  supply  of  gas  than  any  other  furnace 
known.  About  ten  cubic  feet  per  hour  is  sufficient  for  most 
purposes. 

"  Crucibles  must  not  -exceed  2\  by  2  inches.  Any  common 
blowpipe  bellows  will  work  the  furnace  satisfactorily  except  for 
very  high  temperatures  (fusion  of  steel,  etc.),  for  which  a  heavy 
pressure  of  air  is  necessary. 

"  In  adjusting  this  furnace  for  use,  put  the  gauze  nozzle  of  the 
burner  closely  against  the  hole  in  the  side  of  the  casing,  turn  on 
the  gas,  and  light  it  in  the  furnace.  Work  the  bellows  and  then 
put  the  cover  on  the  furnace.  The  air  supply  should  be  such 
that  a  flame  about  two  inches  long  will  play  out  of  the  hole  in 
the  cover,  and  it  may  be  adjusted  by  turning  the  thumb-screw 
on  the  side  of  burner.  The  amount  of  air  and  gas  used  by  this 
burner  is  very  small.  Care  should  be  taken  that  the  right  pro- 
portion of  each  should  be  used.  A  very  light  but  steady  blast 
of  air  will  give  the  best  results. 

"A  modified  pattern  of  the  foregoing  furnace  (Fig.  45)  has 
been  designed,  retaining  all  the  peculiar  advantages  of  the  one 
just  described,  but  burning  refined  petroleum  instead  of  gas 
as  fuel,  and  is  claimed  to  be  equally  as  efficient  as  the  gas 
furnace. 


72  MECHANICAL    DENTISTRY. 

"The  burner  of  this  furnace  is  constructed  upon  the  principle 
of  an  atomizer;  and  this,  of  course,  dispenses  with  a  wick. 
This  method  has  proved  the  most  efficient  of  any  that  has  been 
experimented  with. 

"  The  recent  improvements  consist  in  a  device  for  regulating 
the  supply  of  oil,  which  is  operated  by  the  milled  nut  (marked 
A)  shown  on  top  of  the  reservoir  in  the  cut,  and  the  addition  of 
an  annular  jet  of  air,  which  is  regulated  by  turning  the  sleeve 
(marked  B)." 

An  approved  crucible  furnace  of  recent  introduction,  known 
as  Fletcher's  injector  gas  furnace,  is  shown  in  Fig.  45.  Of  this 
heating  apparatus  Prof.  Essig  *  says  :  "  The  construction  of  this 
apparatus  is  upon  the  principle  of  the  injector  furnace,  and  it  is 

Fig.  45. 


claimed  that  its  power  and  speed  of  working  are  practically 
without  limit,  depending  only  upon  the  gas  and  air  supply. 
With  a  half-inch  gas  pipe  and  the  small  foot  blower  this  furnace 
will  melt  a  crucible  full  of  cast-iron  scraps  in  ten  minutes.  The 
supply  of  gas  required  is  exceedingly  small.  Allowing  five 
cubic  feet  of  gas  for  heating  up,  it  consumes  about  four  feet  of 
gas  for  every  pound  of  cast  iron  melted,  and  for  laboratory  pur- 
poses it  is  the  cheapest  and  most  convenient  furnace  in  use.  It 
is  very  simple  in  construction,  and  consists  of  two  parts,  an 
upper  portion,  which  forms  the  cover,  and  a  lower  part,  which 
holds  the  crucible  while  in  operation." 

A  very  useful  and  almost  indispensable  heating  apparatus  in 

*"  Dental  Metallurgy,"  p.  77. 


GENERATION    AND    APPLICATION    OF    HEAT. 


7: 


Fig.  46. 


the  dental  laboratory,  suitable  for  drying,  boiling,  melting  metals 
requiring  a  moderate  temperature,  as  zinc, 
tin,  lead,  etc.,  heating  flasks  preparatory  to 
packing  with  rubber,  and  a  variety  of  other 
purposes,  is  exhibited  in  Fig.  46. 

The  burner,  consisting,  as  will  be  seen, 
of  a  circular  perforated  gas  tube,  with  a 
central  air  jet,  gives  a  complete  range  of 
temperature,  from  a  gentle  current  of  warm 
air  to  a  clear  red  heat,  and  is  so  perfectly 
under  control  that  a  common  glass  bottle 
may  be  placed  on  the  tripod  and  heated  to 

any  required  temperature  without  the  slightest  risk  of  fracture. 
For  very  low  temperatures  the  ring  must  be  lighted  through 
the  opening  B.  This  gives  a  steady  current  of  heated  air 
through  the  gauze  above.  For  boiling,  melting,  etc.,  the  light 
must  be  applied  on  the  surface  of  the  gauze,  thereby  providing 
a  large  body  of  blue  flame,  which  can  be  urged  by  the  blast 
pipe  C.  This  is  one  of  the  most  generally  useful  burners,  and 
stands  hard,  dirty  work  without  injury.  The  gauze,  if  choked 
up  with  dirt,  can  be  replaced  in  a  few  seconds. 

An  equally  convenient  heater  for  many  purposes  requiring  a 
diminished  temperature,  as  compared  with  the  air-blast  heater 
just  described,  is  exhibited  in  Fig.  47.  A  gentle  current  of  air 
passes  through  side  openings  in  the 
end  of  the  injecting  tube,  mingling 
with  the  gas  supplied  through  a 
rubber  tube  attached  to  an  ordinary 
gas  burner. 

An  admirably  contrived  ladle  fur- 
nace, designed  by  Dr.  Fletcher,  is 
shown  in  Fig.  48.  This  simple  con- 
trivance, provided  with  a  heating  ap- 
paratus similar  to  the  burner  last 
described,  is  especially  well  adapted 
for  melting  any  of  the  several  metals  usually  employed  for  dies 
and  counter-dies,  as  zinc,  tin,  lead,  Babbitt  metal,  etc.  The 
burner  can  be  removed  from  the  casing  and  used  for  other  pur- 
poses  if  desired.     A   cast-iron  ladle   of  suitable   form,   with    a 


Fig.  47. 


74 


MECHANICAL    DENTISTRY, 


detachable  handle,  which  can  be  removed  during  the  process  of 
melting,  is  also  illustrated. 


CRUCIBLES. 

Crucibles  are  small,  conical-shaped  vessels  used  by  the  dentist 
principally  for  the  purpose  of  melting  and  refining  metals  used 
for  plates,  compounding  metallic  alloys,  preparing  and  com- 
pounding the  various  ingredients  employed  in  the  manufacture 
of  porcelain  teeth,  continuous-gum  work,  etc.  They  combine 
in  a  high  degree  the  properties  of  infusibility,  exemption  from 
the  attack  of  substances  fused  in  them,  the  power  of  resist- 
ing sudden  alternations  of  temperature  and  impermeability  to 
fluids  and  gases.     The  Hessian  crucibles,  which    are    in    most 


Fig.  48. 


common  use  among  dentists,  are  composed  of  silica,  alumina, 
and  oxid  of  iron.  Plumbago  crucibles  are  also  made  from 
special  patterns,  and  expressly  designed  for  Fletcher's  furnaces. 
For  a  more  particular  description  of  the  various  components 
entering  into  the  structure  of  crucibles,  as  well  as  the  manner 
of  manufacturing  them,  the  reader  is  referred  to  Piggot's  "Dental 
Chemistry  and  Metallurgy,"  and  other  works  treating  more  fully 
of  the  subject. 

To  avoid  a  possible  loss  of  fused  metals,  which  may  occur  in 
consequence  of  some  imperfection  in  the  crucible,  a  test  trial 
should  be  made  by  placing  in  it  a  small  quantity  of  borax  and 
then  subjecting  it  to  a  high  heat.  If  imperfect,  the  borax, 
rendered  semi-fluid  by  the  heat,  will  pass  through  the  substance 
of  the  crucible  and  elaze  the  surface  on  the  outside. 


CHAPTER  III. 

METALS  EMPLOYED  IX  DENTAL  LABORATORY  OPERATIONS. 

GOLD, 

All  (Aurum). 

Gold  has  been  known  from  a  period  of  great  antiquity,  having, 
according  to  the  writings  of  Moses,  been  wrought  into  articles 
of  jewelry  more  than  three  thousand  years  ago.  As  a  base  or 
support  for  artificial  dentures,  it  has  entirely  superseded  the  use 
of  the  various  animal  substances  formerly  employed,  and,  by  the 
mass  of  practitioners  at  the  present  time,  it  continues  to  be  the 
most  highly  esteemed  metal  for  the  purpose  mentioned,  not- 
withstanding the  more  recent  introduction  of  processes  in  which, 
as  a  base,  this  metal  is  wholly  discarded. 

Gold  is  found  only  in  the  metallic  state,  and  occurs  either 
crystallized  in  the  cube  and  its  allied  forms,  or  in  threads  of 
various  sizes,  twisted  and  interlaced  into  a  chain  of  minute  octa- 
hedral crystals  ;  also  in  spangles  or  roundish  grains.  These  latter, 
when  they  occur  of  a'certain  magnitude,  are  c?ii\&di  pe pitas,  some 
specimens  of  which  have  been  obtained  of  great  size.  In  i8io  a 
mass  of  alluvial  gold  weighing  twenty-eight  pounds  was  found 
in  the  gravel  pits  of  the  creeks  of  Rockhole,  in  North  Carolina. 
A  lump  of  gold  ore  weighing  three  cwt.  was  forwarded  from 
Chili,  South  America,  as  a  contribution  to  the  World's  Exhibi- 
tion in  London.  New  Granada,  California,  Russia,  and  Australia 
have  each  produced  pepitas,  or  masses  of  gold  weighing  respect- 
ively twenty-seven  and  a  half,  twenty-eight,  seventy,  and  one 
hundred  and  six  pounds. 

Geological  Situations. — The  crystalline  primitive  rocks,  the 
compact  transition  rocks,  the  trachytic  and  trap  rocks,  and  allu- 
vial grounds  are  the  formations  in  which  gold  occurs.  Unlike 
many  other  metals,  it  is  never  in  such  large  quantities  as  to 
constitute  veins  by  itself,  but  is  either  disseminated  through  the 

75 


76      '  MECHANICAL    DENTISTRY. 

rocky  masses,  or  spread  out  in  thin  plates  or  grains  on  their 
surface,  or  confined  in  their  cavities  in  the  shape  of  filaments  or 
crystalHzed  twigs.  The  minerals  composing  the  veins  are  either 
quartz,  calcspar,  or  sulphate  of  baryta.  The  ores  associated 
with  the  gold  in  these  veins  are  principally  iron,  copper,  arsen- 
ical pyrites,  galena,  and  blende.  The  most  abundant  sources  of 
gold,  however,  are  in  alluvial  grounds,  where  it  is  found  distrib- 
uted in  the  form  of  spangles  in  the  sands  of  certain  plains  and 
rivers,  especially  at  their  re-entering  angles,  at  the  season  of  low 
water  and  after  storms  and  temporary  floods.  Sufficient  reasons 
have  been  advanced  in  support  of  the  belief  that  gold  found  in 
alluvial  situations  belongs  to  the  grounds  traversed  by  these 
rivers,  instead  of  being  washed,  as  was  formerly  supposed,  from 
the  mountains  in  which  their  waters  have  their  origin. 

Geographical  Distribution. — The  European  mines  more  par- 
ticularly distinguished  for  their  richness  are  in  Hungary  and 
Transylvania,  especially  the  former.  Gold  also  occurs,  but  more 
sparingly,  in  Ireland,  Sweden,  Siberia,  Germany,  Russia,  Spain. 
In  Asia  and  Africa,  the  mines  which  yield  most  abundantly  are 
situated  in  the  southern  portion  of  these  continents.  From  the 
latter,  the  ancients  derived  the  greater  portion  of  their  gold. 
Several  of  the  South  American  provinces  yield  this  metal  in  con- 
siderable quantities.  Washings  are  also  common  in  several 
States  of  the  Union,  but  California  stands  unrivaled,  except  by 
Australia,  in  the  immense  productiveness  of  its  mines,  and  its 
resources  in  respect  to  this  rare  and  valuable  metal  are  reckoned 
inexhaustible. 

Properties  of  Gold. — Pure  gold  is  distinguished  from  all 
other  metals  by  its  brilliant  orange-red  or  yellow  color,  being 
the  only  simple  metal  that  possesses  this  complexion.  It  is 
susceptible  to  a  high  polish,  but  is  inferior  in  brilliancy  to  steel, 
silver,  or  mercury.  Its  specific  gravity  varies  somewhat,  accord- 
ing as  it  is  fused  or  hammered ;  the  former  having  a  density  of 
19.26,  the  latter  ranging  from  19.04  to  19.65.  It  is  only  excelled 
in  density,  therefore,  by  platinum,  the  specific  gravity  of  which 
is  21.25. 

Gold  surpasses  all  other  metals  in  malleability.     The  average 
thickness   of  ordinary  gold   leaf  is   2T2V0T  °^  ^"  inch,  but  the 


METALS  EMPLOYED  IN  DENTAL  LABORATORY  OPERATIONS.  'JJ 

ultimate  degree  of  attenuation  to  which  pure  gold  is  susceptible 
exceeds  considerably  this  estimate.  It  is  also  distinguished  for 
its  ductility.  A  single  grain  of  gold  may  be  drawn  into  wire 
500  feet  in  length,  while  an  ounce  may  be  made  to  extend  1300 
miles.  It  is  somewhat  softer  than  silver,  and  possesses  great 
tenacity,  though  inferior  in  this  quality  to  iron,  copper,  platinum, 
or  silver.  A  thread  of  gold  yofo  of  an  inch  in  diameter  will 
sustain  a  weight  of  150  pounds. 

The  fusing  point  of  gold  is  2016°  F.  It  fuses  with  consider- 
able expansion,  and  on  cooling  contracts  more  than  any  other 
metal. 

On  account  of  the  want  of  affinity  of  gold  for  oxygen,  it 
remains  unaltered  in  the  longest  exposure ;  it  is  incapable  of 
being  oxidized  in  any  heat  that  may  be  applied  to  it,  and  is  only 
volatilized  with  great  difficulty  in  the  resistless  heat  of  the  oxy- 
hydrogen  blowpipe.  It  is  unaffected  by  the  most  concentrated 
of  the  simple  acids,  but  is  readily  soluble  in  aqua  rcgia  or  nitro- 
muriatic  acid  and  nitro-fluoric  acid. 

It  will  thus  be  seen  that  gold  possesses,  in  an  eminent  degree, 
those  general  properti-es  which  render  it  peculiarly  fit  for  the 
purposes  to  which  it  is  applied  in  the  practice  of  dental  pros- 
thesis. 

Influence  of  Alloying  on  the  Properties  of  Gold. — The 
term  alloy  signifies  a  compound  of  any  two  or  more  metals,  as 
brass,  which  is  an  alloy  of  copper  and  zinc. 

Alloys,  in  respect  of  their  uses,  are  practically  new  metals, 
and  differ  in  many  important  respects,  both  in  their  chemical 
and  physical  characteristics,  from  the  constituent  metals  of 
which  they  are  composed.  A  more  particular  account  of  the 
influence  of  alloying  upon  the  general  properties  of  metals,  and 
their  management  and  behavior  in  the  process  of  compounding, 
will  be  given  under  the  head  of  alloys  of  the  baser  metals.  As 
gold  combines  readily  with  most  metals,  some  of  the  more  prom- 
inent conditions  which  distinguish  its  alloys  will  be  given. 

The  malleability  of  gold  is,  strictly  speaking,  always  im- 
paired by  its  union  with  other  metals.  This  effect  is  eminently 
characteristic  of  certain  contaminations,  as  those  with  arsenic, 
tin,  antimony,  bismuth,  lead,  etc. ;  while  with  certain  other  metals, 


78  .  MECHANICAL    DENTISTRY. 

as  silver,  copper,  and  platinum,  unless  in  excess,  this  property 
of  gold  is  so  little  affected,  as  in  no  material  degree  to  interfere 
with  its  being  worked  into  any  desired  form  for  dental  purposes. 
The  ductility  of  gold  is  also  usually  diminished  by  its  incorpora- 
tion with  foreign  metals  ;  sometimes  in  a  remarkable  degree. 
Gold  is  always  rendered  harder,  and  its  tetiacity  is  generally 
increased,  by  alloying,  while  its  detisity  varies  with  the  particular 
metal  or  metals  with  which  it  is  combined.  Thus  the  alloy  of 
gold  with  either  zinc,  tin,  bismuth,  antimony,  or  cobalt,  has  a 
density  greater  than  that  of  the  mean  of  its  constituents,  while 
the  alloys  of  gold  having  a  less  specific  gravity  than  the  mean 
of  their  components  are  those  with  silver,  iron,  lead,  copper, 
iridium,  or  nickel.  Gold  is  ordinarily  more  fusible  when  alloyed, 
the  alloy  always  melting  at  a  less  Jieat  tJian  that  required  to  fuse 
the  most  refractory  constituent,  and  oftentimes  less  than  the  more 
fisible  component.  The  alloy  of  gold  and  platinum  furnishes 
an  example  of  the  former ;  the  platinum,  which  in  its  uncom- 
bined  state  is  infusible  in  the  highest  heat  of  a  blast  furnace, 
forming  a  fusible  compound  with  gold,  the  melting  point  of 
which  is  far  below  that  of  platinum.  Gold  solder,  composed  6f 
gold,  copper,  and  silver,  affords  a  familiar  illustration  of  the 
latter,  the  alloy  melting  at  a  less  heat  than  that  required  to  fuse 
its  least  refractory  component,  silver.  Gold,  which  in  its  pure 
state  has  less  affinity  for  oxygen  than  any  other  metal,  is  ren- 
dered more  or  less  oxidizable  when  combined  with  other  metals. 

That  gold  alloys  tend  to  be  formed  in  definite  proportions  of 
their  constituents  would  appear  from  the  phenomenon  observed 
in  the  native  gold  of  the  auriferous  sands,  which  is  an  alloy  with 
silver  in  the  ratio  of  i  atom  of  silver,  united  to  4,  5 , 6,  or  12  atoms 
of  gold,  but  never  with  a  fractional  part  of  an  atom.  The  same 
circumstance  is  noticed  in  connection  with  the  amalgam  of  silver 
and  mercury.  But  as  alloys  are  generally  soluble  in  each  other, 
the  definiteness  of  this  atomic  combination  is  obscured  and  dis- 
appears in  most  cases. 

Properties  of  Particular  Alloys  of  Gold. — The  metals  with 
which  gold  is  liable  to  be  contaminated  in  the  dental  laboratory 
are  zinc,  tin,  lead,  antimony,  bismuth,  iron  or  steel,  mercury,  and 
arsenic ;    as   also   excess   of  silver,   copper,   and    platinum.     As 


METALS   EMPLOYED   IN   DENTAL  LABORATORY  OPERATIONS.       79 

several  of  these  metals  when  alloyed  with  gold,  even  in  very 
minute  quantities,  are  highly  destructive  in  their  influence  upon 
those  properties  which  adapt  this  metal  to  the  various  wants  of 
the  mechanical  operator,  and  as  their  separation  is  often  attended 
with  considerable  diiTfiCulty,  annoyance,  and  loss  of  time,  it  is 
practically  important  that  care  should  be  taken  to  prevent,  as 
far  as  practicable,  the  admixture  of  any  one  or  more  of  them  with 
the  gold  scrap,  filings,  or  sweepings  that  are  to  be  reconverted 
into  proper  form  for  use.  The  accidental  intrusion  of  these 
metals,  however,  is,  to  some  extent,  unavoidable,  and  as  an 
acquaintance  with  the  more  prominent  characteristics  or  sensible 
properties  of  the  resulting  alloys  sometimes  furnishes  valuable 
indications  in  the  selection  of  the  proper  reagents  employed  in 
their  purification,  a  description  of  individual  alloys  is  introduced. 

Tin,  antimony,  bismuth,  lead,  and  arsenic,  are  peculiarly 
prominent  in  their  effects  upon  the  malleability  of  gold  ;  either 
of  these  metals  in  exceedingly  minute  quantities  render  gold 
intractable. 

One  part  of  antimony  with  nine  parts  of  gold,  form  a  pale, 
bfittle  alloy,  and  in  the  proportion  of  one  part  of  the  former  to 
1920  of  gold,  the  resulting  compound  is  too  brittle  to.  admit  of 
successful  lamination.  i 

An  alloy  of  arsenic  with  gold  containing  ^tit  ^^  "^^  former  is 
a  gray,  brittle  metal,  while  in  the  proportion  of  9^^,  the  mallea- 
bility of  the  gold  is  seriously  impaired  without  suffering  any 
change  of  color.  So  energetic  is  the  influence  of  this  metal  On 
gold  that  the  latter  is  rendered  brittle  when  subjected  even  to 
the  vapor  of  arsenic. 

Tin,  lead,  and  bismuth  are  somewhat  analogous  to  arsenic 
in  their  influence  upon  the  malleability  of  gold,  either  of  them, 
in  almost  inappreciable  quantities,  rendering  the  latter  metal 
unmanageable  under  the  rollers.  One  part  of  lead  or  bismuth 
to  1920  of  gold  converts  the  latter  into  an  unmalleable  metal, 
while  tin  exceeds  either  in  its  remarkable  tendency  to  render 
gold  hard  and  brittle.  Alloys  of  gold  with  tin  are  of  a  light 
color ;  those  with  lead  are  of  a  darker  complexion. 

Zinc  with  gold  forms  a  brittle  alloy,  and  when  combined  in 
equal  proportions  is  exceeding  hard,  white,  and  brittle.     Uniting 


80  MECHANICAL    DENTISTRY. 

or  incorporating  itself  less  intimately  with  the  gold  than  either 
lead  or  tin,  however,  it  not  infrequently  happens  that  portions 
of  the  ingot  will  be  brittle  while  others  remain,  in  some  degree, 
malleable ;  so  that  the  bar,  when  rolled  out  in  the  form  of 
plate,  will  be  perforated  or  cracked  at  those  points  where  the 
zinc  predominates,  while  remaining  portions  of  the  plate  retain 
a  moderate  degree  of  softness  and  pliability. 

The  working  properties  of  gold  are  not  sensibly  affected  by 
the  incorporation  of  very  small  quantities  of  iron,  as  an  alloy  of 
these  metals,  in  the  proportion  of  one  part  of  the  latter  to  eleven 
of  gold,  remains  malleable. 

Platinum,  in  itself  a  highly  refractory  metal,  is,  as  before 
stated,  rendered  fusible  in  combination  with  other  metals.  When 
combined  with  gold  in  small  proportions,  the  latter  is  rendered 
harder  and  more  elastic  without  having  its  malleability  practic- 
ally impaired.  Platinum  very  readily  affects  the  color  of  gold, 
the  smallest  quantities  rendering  the  alloy  pale  and  dull- 
colored. 

Silver  unites  with  gold  in  every  proportion,  and  is  the  chief 
metal  employed  in  the  reduction  of  gold  to  the  required 
forms  for  dental  uses.  It  renders  gold  more  fusible,  and  imparts 
to  it  increased  hardness  without  materially  affecting  its  mallea- 
bility. The  alloy  is  light-colored  in  proportion  to  the  amount 
of  silver  introduced. 

Copper,  like  silver,  is  usually  combined  with  gold  in  the  for- 
mation of  plate,  solders,  etc.,  and  hardens  and  renders  gold 
tougher  without  practically  impairing  its  malleability.  It 
imparts  to  the  alloy  a  deeper  red  color,  and  in  the  form  of  plate 
is  capable  of  receiving  a  polish  excelling  in  richness  and  bril- 
liancy any  other  metal. 

The  foregoing  alloys  of  gold,  it  will  be  perceived,  are  such  as 
result  from  the  incorporation  with  gold  of  minute  proportions 
of  any  one  of  the  base  metals  mentioned,  and  possess  certain 
physical  characteristics  that  indicate,  with  tolerable  certainty, 
the  particular  alloying  component.  Thus,  for  example,  if  the 
alloy  is  light-colored  and  very  brittle,  the  presence  of  tin  may 
be  suspected  ;  if  brittle  and  dull-colored,  lead  is  indicated  ;  if 
grayish  or  dull-colored,  but  still   malleable,  tough  and  elastic. 


*  METALS  EMPLOYED  IN   DENTAL  LABORATORY  OPERATIONS.       8  I 

platinum  is   probably  present ;  if  unequally  malleable,  or  brittle 
in  spots,  the  presence  of  zinc  may  be  inferred. 

Alloys  of  gold,  however,  embracing  several  or  all  of  these 
metals  in  varying  proportions,  are  sometimes  accidentally 
formed,  in  which  case  the  more  distinctive  features  which 
characterize  the  binary  compounds  are  lost  or  obscured. 


CHAPTER  IV. 

REFINING  GOLD. 

Elements  Employed. — The  separation  of  foreign  metals 
from  gold  by  what  is  termed  the  "  dry  method,"  or  roasting,  is 
effected  by  the  action  on  them  of  either  oxygen,  chlorin,  or 
sulphur,  converting  them  into  oxids,  chlorids,  or  sulphurets. 
Certain  compound  substances  are  used  for  this  purpose  which, 
when  heated  and  decomposed,  yield  these  elements  in  sufficient 
quantities  for  the  purposes  specified.  The  refining  agents  in 
common  use  are  nitrate  of  potassa  (nitre,  or  saltpetre),  which 
yields  oxygen  ;  cJilorid  of  mercury  (corrosive  sublimate),  which 
yields  chlorin ;  and  sulpliuret  of  antimony  (crude  antimony), 
which  yields  sulphur.  Other  compounds  contain  these  elements, 
but  those  mentioned  are  generally  preferred  because  they  con- 
tain them  abundantly,  are  readily  decomposed  by  heat,  and  do 
not  materially  interfere  with  the  process  of  separation  by  the 
introduction  of  troublesome  components  into  the  alloy. 

Before  considering  specifically  the  different  modes  of  refining 
alloys  of  gold,  it  will  be  convenient  to  classify  the  different  forms 
of  gold  as  they  occur  in  working  this  metal  in  the  laboratory. 

1.  Plate-scrap  or  clippings,  and  plate-filings.  These,  if  proper 
care  is  taken  to  prevent  the  introduction  of  fragments  of  platinum, 
impure  filings,  or  particles  of  base  metals,  only  require,  provided 
they  were  originally  of  suitable  fineness,  to  be  remelted  and 
again  converted  into  plate  or  other  forms  for  use. 

2.  Mixed  filings,  and  fragments  containing  solder,  platinum, 
etc.  These,  when  melted  alone,  produce  an  alloy  more  or  less 
impoverished  in  proportion  to  the  quantity  and  quality  of  the 
foreign  metals  introduced  in  finishing  pieces  constructed  of  gold, 
and  should  either  be  separately  refined  by  roasting,  or  reduced 
to  pure  gold  by  the  "  humid  method,"  to  be  described  hereafter. 

3.  Sweepings.  This  form  embraces  many  impurites,  earthy 
and  metallic,  and  should  first  be  thoroughly  washed,  to  remove 

82 


REFINING    GOLD.  83 

the  earthy  constituents,  after  which  the  remaining  metals  may 
either  be  mixed  with  class  second,  or  separately  refined.  Another 
and  perhaps  better  method,  is  to  fuse  together  the  sweepings 
and  substances  hereinafter  mentioned,  in  the  following  propor- 
tions :  Of  sweepings,  eight  parts  ;  chlorid  of  sodium,  four  parts  ; 
impure  carbonate  of  potassa,  four  parts ;  impure  supertartrate 
of  potassa,  one  partj  and  nitrate  potassa,  half  part.  Mix  themi 
thoroughly  together,  and  melt  in  a  crucible.  The  crucible  with 
its  contents  should  remain  in  the  fire  for  some  time,  in  order  to 
secure  a  complete  separation  of  the  metals  from  extraneous 
matter. 

It  is  evident  from  the  above  classification  that  much  time  and 
labor  may  be  saved  by  preserving  these  forms  of  gold  separately 
as  they  accumulate  in  the  laboratory.  Separate  lap-skins  or  recep- 
tacles, therefore,  should  be  appropriated  to  the  working  of  gold, 
one  to  receive  scrap  and  unmixed  plate-filings,  which  may  be 
reconverted  into  plate  without  refining;  another  to  collect  the 
solder-filings,  and  such  impure  fragments  as  require  puri- 
fication. 

Separation  of  Foreign  Metals  from  Gold. — The  most 
troublesome  ingredients  which  find  their  way  into  gold  alloys  are 
what  are  commonly  called  Inisc  metals,  as  tin,  lead,  zinc,  iron, 
antimony,  bismuth,  etc..  In  attempting  to  separate  these  metals 
from  gold,  it  is  not  a  matter  of  indifference  what  reagent  is  em- 
ployed, inasmuch  as  distinct  affinities  exist,  which  may  be  ad- 
vantageously consulted.  If,  for  example,  zinc  or  iron  or  both 
of  these  metals  are  present  in  small  quantities,  any  compound 
which  yields  oxygen  will,  by  virtue  of  the  affinity  of  the  latter 
for  these  metals,  effect  their  separation  by  converting  them  into 
oxids  ;  hence,  when  these  metals  are  to  be  got  rid  of,  nitrate  of 
potassa  is  employed.  But  oxygen  has  a  feeble  affinity  for  tin, 
and  when  this  metal  is  present,  its  separation  is  better  effected 
by  some  compound  which  parts  with  chlorin  in  the  act  of  de- 
composition;  chlorid  of  mercury  is  therefore  used  for  the  pur- 
pose. When  the  alloy  of  gold  contains  a  number  of  these 
metals  at  the  same  time,  and  is  very  coarse,  sulphuret  of  anti- 
mony, which  is  a  very  powerful  and  efficient  reagent,  should  be 
resorted  to,  unless  the  operator  should  prefer,  and  which  is  the 


84  MECHANICAL    DENTISTRY. 

better  way,  to  reduce  the  alloy  to  pure  gold  by  the  "  humid 
method." 

The  Dry  Method. — After  all  traces  of  iron  or  steel  have  been 
removed  from  the  gold  fragments  and  filings  by  passing  a  mag- 
net repeatedly  through  them,  the  latter  should  be  placed  in  a 
clean  crucible,  lined  on  the  inside  with  borax,  and  covered  either 
with  a  piece  of  fire-clay  slab,  or  broken  crucible.  Sheet-iron 
has  been  recommended  for  the  latter  purpose,  but  should  never 
be  used,  as,  when  highly  heated,  scales  form  on  the  surface,  and  are 
liable  to  drop  in  upoti  the  fused  metals.  If  the  operation  is  likely 
to  be  protracted,  an  inverted  crucible,  with  a  hole  in  the  bot- 
tom, may  be  securely  luted  to  the  top  of  the  one  containing  the 
metals  ;  the  refining  agents  and  fluxes  being  introduced  through 
the  opening  in  the  upper  crucible.  These  are  then  placed  in  the 
furnace,  on  a  bed  of  charcoal,  or  what  is  better,  a  mixture  of 
charcoal  and  coke,  the  latter  being  built  up  around  the  crucible, 
and  over  it  when  covered  with  a  second  crucible,  care  being 
taken  that  no  fragments  of  fuel  are  permitted  to  fall  in  upon  the 
fused  metals.     The  process  is  as  follows  : — 

First  melt  the  alloy  at  a  high  temperature,  to  oxidize 
the  base  metals ;  the  refining  agents  may  then  be  added  in 
small  quantities  from  time  to  time,  and  the  heat  continued  from 
half  an  hour  to  an  hour,  according  to  the  coarseness  of  the 
alloy.  The  agents  first  employed  are  borax,  and  potassium 
nitrate  (KNO3).  The  latter  assists  the  oxidation  by  parting 
with  its  oxygen,  when  the  foreign  metals  will  generally  become 
entirely  oxidized  and  dissolved  in  the  slag. 

The  crucible  should  be  removed  from  the  fire,  and  the  metals 
allowed  to  cool  gradually.  The  crucible  may  now  be  broken 
and  the  button  of  gold  at  the  bottom  removed  and  separated 
from  the  slag  that  covers  it  with  a  hammer.  The  gold  should 
then  be  put  into  a  fresh  crucible  and  remelted  for  pouring  into 
ingot-moulds,  which  should  be  previously  warmed  and  oiled  (see 
page  97).  This  treatment,  with  nitrate  of  potassa  and  borax,  will 
usually  be  sufficient,  as  most  metals  are  oxidizable.  If,  however, 
after  hammering,  annealing,  and  rolling  the  ingot,  it  should  still  be 
found  brittle,  it  must  be  remelted,  and  some  other  refining  agent 
employed  to  remove  the  traces  of  the  base  metals.    If  it  is  known 


REFINING    GOLD.  85 

what  foreign  metal  is  present,  the  particular  reagent  which  will 
most  readily  attack  it  should  be  used.  But  if,  as  is  often  the  case, 
the  alloy  is  of  uncertain  composition,  or  contains  several  metals 
having  distinct  affinities,  the  process  becomes  to  some  extent 
experimental,  making  it  necessary  to  use  first  one  refining  agent 
and  then  another,  until,  from  the  appearance  and  the  manipula- 
tion of  the  gold,  it  is  found  to  be  free  from  alloy.  The  special 
regents  employed  are  as  follows  : — 

When  tin  or  lead  is  present,  add  mercuric  chlorid,  HgCl2 
(corrosive  sublimate),  and  zinc  chlorid,  ZnCh,  or  lead  chlorid, 
PbClj,  are  formed  and  with  the  mercury  volatiHzed  by  the  heat. 

"When  silver  is  present,  add  to  the  molten  alloy  from  two  to 
four  times  its  weight  of  antimony  sulphid,  SbzSa ;  this  must  be 
added  carefully  and  a  little  at  a  time.  The  heat  decomposes  the 
sulphid.  The  sulphur  unites  with  the  silver  and  other  base 
metals,  forming  sulphids,  while  the  antimony  unites  with  the 
gold,  forming  a  leaden -colored  alloy.  When  effervescence  has 
ceased,  remove  the  crucible  from  the  fire  and  allow  it  to  cool. 
The  antimony  and  gold  alloy  will  be  found  in  the  bottom  of  the 
crucible,  and  the  sulphids  on  the  surface. 

To  separate  the  antimony  from  the  gold,  remelt  the  alloy 
and  throw  upon  the  molten  mass  a  current  of  air  from  a  blow- 
pipe. Antimony  oxid,  Sb^Os,  is  formed  and  volatilized;  continue 
the  process  until  fumes  cease  to  be  given  off. 

When  iridium  is  present.  Prof.  Essig,  in  writing  upon  the 
subject,  says  :  "  The  little,  hard  grains  occasionally  met  with  in 
gold,  upon  which  the  file  m.akes  no  impression,  consist  of  iridium, 
or  a  native  alloy  of  osmium  and  iridium,  and  are  not  combined 
with  the  gold,  but  merely  disseminated  through  it.  The  only 
dry  method  of  separating  it  from  gold  consists  in  alloying  the 
latter  with  three  times  its  weight  in  silver,  by  which  means  the 
specific  gravity  of  the  metal  is  so  much  lowered  that  iridium, 
which  is  very  infusible  and  of  a  specific  gravity  of  21.1,  will  sub- 
side to  the  bottom  of  the  crucible,  when  the  gold  and  silver  alloy 
may  be  poured  or  ladled  off.  As  some  of  the  gold  will  remain 
with  the  residue,  more  silver  must  be  melted  with  it,  the  opera- 
tion  being  repeated   several  times   until   nearly  all  the   gold  is 


86  MECHANICAL    DENTISTRY. 

removed."  The  gold  and  silver  alloy  may  then  be  separated  as 
directed  above. 

When  platinum  is  present.  If,  after  treating  the  alloy  with 
the  reagents  enumerated,  it  should  be  found  malleable,  but  stiff 
or  elastic,  and  of  a  rather  dull  color,  it  is  due  to  the  presence  of 
platinum  ;  and  any  further  attempts  to  reduce  it  by  the  "  dry 
process  "  will  prove  unavailing.  It  miist  then  be  subjected  to 
what  will  hereafter  be  described  as  the  "  humid  or  wet  method." 

The  Humid  Method. — When  it  is  desired  to  reduce  the  alloy 
to  pure  gold,  which  is  generally  advisable  whenever  the  gold  to 
be  refined  consists  of  very  coarse  filings,  fragments  of  plate  con- 
taining large  quantities  of  solder,  linings  with  platinum  pins 
attached,  particles  of  base  metals,  etc.,  the  "  humid  or  wet 
method,"  as  it  is  called,  should  be  employed.  The  solvents  in 
common  use  for  this  purpose  are  nitric,  sulphuric,  and  nitro- 
muriatic  or  hydrochloric  acid ;  but  as  the  desired  results  can  be 
more  conveniently  and  directly  obtained  by  the  use  of  the  latter, 
or  hydrochloric  acid,  this  most  available  method  alone  will  be 
given.  The  following  practical  remarks  on  the  subject  are  from 
an  article  on  the  "  Management  of  Gold,"*  by  Professor  George 
Watt  :— 

"  When  the  alloy  is  composed  of  metals  differing  but  little  in 
their  affinities  for  oxygen,  chlorin,  etc.,  we  resort  to  one  of  the 
'  wet  methods.'  And,  in  connection,  wt  will  only  describe  the 
one  which  we  consider  the  most  convenient  and  effectual  for  the 
practical  dentist.  It  is  effectual  in  all  cases,  as  it  always  gives 
us  pure  gold. 

■'  Let  us,  then,  suppose  that  our  gold  alloy  has  become  contam- 
inated with  platinum  to  such  an  extent  that  the  color  and  elas- 
ticity of  the  plate  are  objectionable.  The  alloy  should  be  dis- 
solved in  nitro-muriatic  or  hydrochloric  acid,  called  ac/na  regia. 
The  best  proportions  for  aqua  regia  are  three  parts  of  hydro- 
chloric acid  to  one  of  nitric.  If  the  acids  are  at  all  good,  four 
ounces  of  the  aqua  regia  will  be  an  abundance  for  an  ounce  of 
the  alloy.      The  advantage  of  using  the  acids  in  the  proportion 

*  Dental  Register  of  the  West,  vol.  xii,  p.  251. 


REFINING    GOLD.  8/ 

of  three  to  one,  instead  of  two  to  one,  as  directed  in  most  of  the 
text-books,  is,  that  when  the  solution  is  completed  there  is  but 
little,  if  any,  excess  of  nitric  acid.  If  the  acids  be  *  chemically 
pure,'  four  parts  of  the  hydrochloric  to  one  of  the  nitric  produces 
still  better  results. 

"  By  this  process  the  metals  are  all  converted  into  chlorids ; 
and,  as  the  chlorid  of  silver  is  insoluble,  and  has  a  greater 
specific  gravity  than  the  liquid,  it  is  found  as  a  grayish-white 
powder  at  the  bottom  of  the  vessel.  The  chlorids  of  the  other 
metals,  being  soluble,  remain  in  solution.  By  washing  and 
pouring  off,  allowing  the  chlorid  of  silver  time  to  settle  to  the 
bottom,  the  solution  may  be  entirely  separated  from  it. 

"The  object  is  now  to  precipitate  the  gold  while  the  others 
remain  in  solution.  This  precipitation  may  be  effected  by  any 
one  of  several  different  agents,  but  we  will  mention  only  the 
protosulphate  of  iron. 

"  This  salt  is  the  common  green  copperas  of  the  shops,  and,  as 
it  is  always  cheap  and  readily  obtained,  we  need  look  no  further. 
It  should  be  dissolved  in  clean  rain-water,  and  the  solution 
should  be  filtered,  and"  allowed  to  settle  until  perfectly  clear. 
Then  it  is  to  be  added  gradually  to  the  gold  solution  as  long  as 
a  precipitate  is  formed,  and  even  longer,  as  an  excess  will  the 
better  insure  the  precipitation  of  all  the  gold.  The  gold  thus 
precipitated  is  a  brown  powder,  having  none  of  the  appearances 
of  gold  in  its  ordinary  state.  The  solution  should  now  be 
filtered,  or  the  gold  should  be  allowed  to  settle  to  the  bottom, 
where  it  may  be  washed  after  pouring  off  the  solution.  It  is 
better  to  filter  than  decant  in  this  case,  as,  frequently,  particles 
of  the  gold  float  on  the  surface,  and  would  be  lost  in  the  wash- 
ings by  the  latter  process. 

"  Minute  traces  of  iron  may  adhere  to  the  gold  thus  precipi- 
tated. These  can  be  removed  by  digesting  the  gold  in  dilute 
sulphuric  acid  ;  and,  when  the  process  is  properly  conducted  thus 
far,  the  result  is  pure  gold,  w^hich  may  be  melted,  under  carbon- 
ate of  potash,  in  a  crucible  lined  with  borax,  and  reduced  to  the 
required  carat." 


CHAPTER  V. 
ALLOYS  OF  GOLD  FOR  DENTAL  PURPOSES. 

Gold  in  its  pure  state  is  rarely  employed  by  the  dentist  in 
laboratory  processes,  on  account  of  its  softness  and  flexibilit)' ; 
it  is,  therefore,  usually  alloyed  with  such  metals  as  impart  to  it 
— without  practically  impairing  either  its  malleability,  pliancy  or 
purity — the  degree  of  hardness,  strength  and  elasticity  necessary 
to  resist  the  wear  and  strain  to  which  an  artificial  piece  con- 
structed from  it  is  unavoidably  exposed  in  the  mouth. 

Reducing  Metals. — The  metals  with  which  gold  is  usually 
combined  are  copper  and  silver.  It  is  sometimes  reduced  with 
silver  alone,  many  regarding  the  introduction  of  copper  into  the 
alloy  as  objectionable,  as  plate  derived  from  it  is  supposed  to  be 
more  readily  tarnished  and  to  communicate  to  the  mouth  a  dis- 
agreeable metallic  taste.  This  is  unquestionably  j:rue  if,  as  is 
sometimes  the  case,  the  copper  used  is  in  excess;  when,  in  addi- 
tion to  the  effects  mentioned,  gold,  so  debased,  may  become  a 
source  of  positive  injury  to  the  organs  of  the  mouth,  as  well  as 
to  the  general  health.  The  small  proportions  of  copper  usually 
employed  in  forming  gold  plate,  however,  are  not  likely  to  pro- 
duce in  any  objectionable  degree  the  consequences  complained 
of,  unless  the  fluids  of  the  mouth  are  greatly  perverted.  If  gold 
coin  is  used  in  the  formation  of  plate,  it  may  be  sufficient  to 
add  silver  alone,  inasmuch  as  copper  is  already  present ; 
though,  usually,  additional  quantities  of  the  latter  metal  are 
added. 

Required  Fineness  of  Gold  Plate. — Alloys  of  gold  to  be 
permanently  worn  in  the  mouth  should  be  of  such  purity  as 
will  most  certainly,  under  all  the  contingencies  of  health  and 
disease,  resist  any  chemical  changes  that  would  tend  to  com- 
promise either  the  comfort  or  health  of  the  patient.  Evils  of  no 
inconsiderable  magnitude  are  sometimes  inflicted,  either  through 

88 


ALLOYS  OF  GOLD  FOR  DENTAL  PURPOSES,  89 

ignorance,  carelessness  or  cupidity,  by  a  disregard  of  this  impor- 
tant requirement.  If  the  general  health  of  the  patient  remained 
always  uniformly  unimpaired,  with  the  secretions  of  the  mouth  in 
their  normal  state,  gold  degraded  to  eighteen  or  even  sixteen 
carats  fine,  would  undergo  no  material  changes  in  the  mouth. 
But  it  must  be  remembered  that,  in  addition  to  the  corrosive 
agents  introduced  into  the  mouth  from  without,  a  variety  of  dis- 
eases, local  and  constitutional,  effect  important  changes  in  the 
otherwise  bland  and  innoxious  fluids  contained  therein,  which, 
from  being  alkaline  or  neutral,  become  more  or  less  acidulated. 
Indigestion,  with  acid  eructations  ;  gastro-enteritis  ;  ague  ;  inflam- 
matory and  typhoid  fevers ;  brain  affections  ;  eruptive  diseases  ; 
rheumatism;  gout,  etc.,  are  some  of  the  local  and  constitutional 
disorders  almost  uniformly  impartingto  the  mucous  and  salivary 
secretions  an  acid  reaction.  When  this  condition  of  the  secretions 
exists  in  connection  with  the  use  of  gold  readily  acted  on  chem- 
ically by  reason  of  its  impoverishment,  some  degree  of  irritation 
of  the  tissues  of  the  oral  cavity  is  likely  to  ensue.  Gold  plate 
intended  to  be  introdiiced  into  the  mouth  should  not,  therefore, 
as  a  general  thing,  be  of  a  less  standard  of  fineness  than  from 
eighteen  to  twenty  carats.  It  may  exceed  this  degree  of  purity 
in  some  cases,  but  will  rarely  or  never,  unless  alloyed  with 
platinum,  admit  of  being  used  of  a  higher  carat  than  the  pres- 
ent American  coin,  which  is  21.6  carats  fine.  , 

Formulas  for  Gold  Plate  used  as  a  Base  for  Artificial 
Dentures. — Any  of  the  following  formulas  may  be  employed 
in  the  formation  of  gold  plate  to  be  used  as  a  base  or  support 
for  artificial  dentures.  The  relative  proportions  of  the  alloying 
components  may  be  varied  to  suit  the  peculiar  views  or  neces- 
sities of  the  manipulator.  The  estimated  carat  of  the  appended 
formulas  is  based  on  the  fineness  of  the  American  gold  pieces 
coined  in  1837  and  thereafter. 

GOLD    PLATE    EIGHTEEN    CARATS    FINE. 

Fortmda  No.  I.  Forviula  No.  2. 

18  dwts.  pure  gold,  20  dwts.  gold  coin, 
4  dwts.  fine  copper,  2  dwts.  fine  copper, 

2  dwts.  fine  silver.  2  dwts.  fine  silver. 


90  MECHANICAL    DENTISTRY. 

GOLD   PLATE   NINETEEN  CARATS    FINE. 

Formula  No.  3.  Formula  No.  4. 

19  dwts.  pure  gold,  20  dwts.  gold  coin, 
3  dwts.  copper,  25  grs.  copper, 

2  dwts.  silver.  40  -\-  grs.  silver. 

GOLD    PLATE   TWENTY    CARATS    FINE. 

Formula  N^o.  5-  Forntula  No.  6. 

20  dwts.  pure  gold,  20  dwts.  gold  coin, 
2  dwts.  copper,  18  grs.  copper, 

2  dwts.  silver.  20  -\-  grs.  silver. 

GOLD    PLATE   TWENTY-ONE   CARATS    FINE. 

Formula  No.  7.  Formula  No.  8.                  Fortmda  N^o.  9. 

21  dwts.  pure  gold,  20  dwts.  gold  coin,  20  dwts.  gold  coin, 

2  dwts.  copper,  'S'Tgrs.  silver.                   6  grs.  copper, 

I  dwt.  silver.  74  grs.  platinum. 

GOLD    PLATE   TWENTY-TWO   CARATS    FINE. 

Formula  No.  10. 
22  dwts.  pure  gold, 

I  dwt.  fine  copper, 
18  grs.  silver, 

6  grs.  platinum. 

The  union  of  platinum  with  gold,  as  in  Formula  No.  10,  fur- 
nishes an  alloy  rich  in  gold,  while  it  imparts  to  the  plate  derived 
from  it  a  reasonable  degree  of  stiffness  and  elasticity  ;  preserves 
in  a  good  degree  the  characteristic  color  of  fine  gold  ;  and  does 
not  materially  impair  its  susceptibility  of  receiving  a  high  polish. 
The  amount  of  gold  coin  given  in  Formula  No.  9  may  be  reduced 
with  platinum  alone,  adding  to  it  from  eight  to  twelve  grains ; 
in  which  case,  although  the  carat  of  the  alloy  is  lowered,  its 
absolute  purity  remains  unaffected,  and  plate  formed  from  it  will 
better  resist  any  changes  in  the  mouth  than  gold  coin  itself 

formulas  for  Gold  Plate  used  for  Clasps,  "Wire,  Stays  or 
Linings,  Metallic  Pivots,  etc. — Gold  used  in  the  formation  of 
clasps,  stays,  etc.,  is  improved  for  these  purposes  by  the  addition 
of  sufficient  platinum  to  render  it  firmer  and  more  elastic  than 
the  alloys  ordinarily  employed  in  the  formation  of  plate  as  a 


ALLOYS  OF  GOLD  FOR  DENTAL  PURPOSES.  9 1 

base.  The  advantages  of  this  elastic  propefty,  in  its  application 
to  the  purposes  under  consideration,  are,  that  clasps  formed  from 
such  alloys  will  adapt  themselves  more  accurately  to  the  teeth, 
as,  when  partially  spread  apart  on  being  forced  over  the  crowns, 
they  will  spring  together  again  and  accurately  embrace  the  more 
contracted  portions.  In  the  form  of  stays  or  backings,  additional 
strength  being  imparted,  a  less  amount  of  substance  will  be 
required  ;  the  elasticity  of  these  supports,  also,  will  not  only 
lessen  the  chances  of  accident  to  the  teeth  themselves  in  masti- 
cation and  otherwise,  but  preserve  their  proper  position  when 
temporarily  disturbed  by  any  of  the  forces  applied  to  them. 
The  same  advantages  last  mentioned  are  obtained  from  this 
property  in  the  use  of  metallic  pivots. 

Formula  No.  i.  Formula  No.  2. 

20  dwts.  pure  gold,  20  dwts.  coin  gold, 
2  dwts.  fine  copper,  8  grs.  fine  copper, 

I  dwt.  fine  silver,  10  grs.  silver. 

I  dwt.  platinum.  20  grs.  platinum. 

The  alloy  derived  from  either  of  these  formulas  will  be  twenty 
carats  fine. 

Gold  Solders.— Solders  are  a  class  of  alloys  by  means  of 
which  the  several  pieces  of  the  same  or  of  different  metals  are 
united  to  each  other.  They  should  be  more  fusible  than  the 
metals  to  be  united,  and  should  consist  of  such  components  as 
possess  a  strong  affinity  for  the  substances  to  be  joined.  They 
should  also  be  as  fine  as  the  metals  to  which  they  are  applied 
will  admit  of  without  endangering  the  latter.  Solders  of  dif- 
ferent degrees  of  fineness,  therefore,  should  always  be  provided, 
from  which  the  one  most  suitable  for  any  given  case  may  be 
selected. 

The  use  of  solders  of  doubtful  or  unknown  composition  should 
be  avoided,  and  hence  they  should  be  compounded  either  from 
pure  gold  or  gold  coin. 

The  following  formula  taken  from  Prof  Harris's  work  on 
"  Dental  .Surgery,"  page  666,  recipe  No.  3,  may  be  used  in  con- 
nection with  eighteen-  or  twenty-carat  gold  plate,  and  is  sixteen 
carats  fine  : — 


92  MECHANICAL    DENTISTRY. 

6  dwts.  pure  gold, 
2  dwts.  rosette  copper, 
I  dwt.  fine  silver. 

Recipes  Nos.  i  and  2,  page  663  of  same  work,  are  too  coarse 
to  be  introduced  into  the  mouth  ;  the  former  being  a  fraction 
below  fourteen  carats,  while  the  latter  is  still  more  objectionable, 
exceeding  but  little  twelve  and  one-half  carats. 

Formula  No.  i  of  the  following  recipes  is  a  fraction  over 
fifteen  carats  fine :  and  No.  2  furnishes  a  solder  eighteen  carats 
fine : — 

Formula  No.  I.  Fornnda  No.  2. 

6  dwts.  gold  coin,  Gold  coin,  30  parts. 

30  grs.  silver,  Silver,  4     " 

20  grs.  copper,  Copper,         i     " 

10  grs.  brass.  Brass,  i     " 

In  the  reduction  of  gold  for  solders.  Dr.  Dorrence  recom- 
mends the  use  of  what  he  calls  "  solder  alloy."  This  is  derived 
from  the  following  formula  : — 

1  part  pure  silver, 

2  parts  pure  zinc, 

3  parts  pure  copper. 

The  copper  and  silver  are  melted  without  flux,  in  a  clean  cru- 
cible which  is  well  lined  with  borax ;  the  zinc  is  then  added  in 
small  quantities  as  rapidly  as  maybe  without  chilling  the  molten 
mass  so  that  it  loses  its  fluidity,  meanwhile  stirring  it  with  a 
clay  pipe-stem  or  rod,  or  a  white-wood  stick,  until  the  profuse 
fumes  of  the  burning  zinc  just  pass  off,  when  pour  immediately 
into  an  ingot  mold,  or  into  clean  water  in  a  clean  wooden 
pail.  The  metals  entering  into  the  composition  of  this  solder 
alloy  should  be  absolutely  pure,  especially  should  they  be 
free  of  arsenic,  antimony,  cadmium,  etc.,  in  which  case  not  only 
the  alloy,  but  gold  and  silver  solders  made  from  it,  will  be  tough 
and  easy-flowing.  Inasmuch  as  the  zinc,  in  compounding  the 
alloy,  has  not  been  protected  from  oxidation,  if  it  has  been  cast 
at  the  proper  moment,  it  will  be  found  present  in  about  its  com- 
bining weight.  Both  gold  and  silver  solders  made  with  this 
alloy  will,  as   has  been   stated,  be  found  very  tough,  and  easy- 


ALLOYS  OF  GOLD  FOR  DENTAL  PURPOSES.  93 

flowing,  the  range  of  proportion  most  desirable  being,  for  gold 
solder,  from  20  to  12  carats,  or  from  15  to  50  per  cent,  of  alloy. 
Dr.  D.  very  properly  says,  however,  that  the  12  carat  or  50  per 
cent,  solder  is  too  coarse  for  dental  work.  From  10  to  15  per 
cent,  of  the  alloy  added  to  gold  coin  is  recommended  as  a  suit- 
able solder  in  the  construction  of  coin-gold  crowns.  ~- — ^ 

Zinc,  as  a  constituent  of  solders,  is  used  principally  with  a 
view  of  rendering  them  more  fusible  without  materially  debas- 
ing'them  if  the  proper  proportion  is  observed.  Its  employment 
under  any  circumstances  has  been  objected  to  by  some,  on  the 
ground  that  the  alloy  is  more  readily  tarnished  in  the  mouth,  is 
more  brittle,  and  that  it  furnishes  more  favorable  conditions  for 
galvanic  action.  These  objections  only  hold  good  when  zinc  is 
used  in  excess.  When  employed  in  quantities  sufficient  only  to 
make  the  gold  flow  readily  and  evenly  at  a  diminished  heat,  it  is 
claimed  that  the  base  metal  used  in  these  alloys  is  chiefly  con- 
sumed in  the  process  of  soldering,  leaving  a  residuum  of  gold 
alloy  equal,  or  nearly  so,  in  purity  to  solder  not  so  contaminated. 
If  such  is  the  case,  they  are  acceptable  alloys  for  soldering  pur- 
poses, inasmuch  as  it  is  not  only  desirable  to  have  an  easy-flow- 
ing solder,  but  one  which  shall  have  as  little  affinity  as  possible 
for  acids  often  found  associated  with  the  fluids  of  the  mouth. 
Care  should  be  taken  to  add  no  more  zinc  than  is  necessary  to 
make  the  solder  flow  freely  under  a  heat  that  may  be  safely 
applied  without  danger  of  melting  the  pieces  to  be  united. 

Method  of  reducing  Gold  to  a  lower  or  raising  it  to  a 
higher  standard  of  Fineness,  and  of  determining  the  Carat  of 
any  given  Alloy. — In  the  process  of  compounding  gold  for 
dental  purposes,  the  manipulator  should  always  aim  at  exactness 
in  the  quantity  and  relative  proportions  of  the  reducing  com- 
ponents, and  should  be  able  to  determine  precisely  the  purity  of 
the  metals  he  employs.  Gold  alloys  are  too  often  arbitrarily 
compounded,  and  used  without  any  adequate  knowledge  of  their 
qualities  or  properties  ;  and  formulas,  taken  on  trust,  are  em- 
ployed without  any  certain  knowledge  of  the  quality  of  the 
alloys  they  produce. 

That  we  may  know  certainly  the  quality  of  the  gold  alloys 
used  in  the  laboratory  without  resorting  to    the    inconvenient 


94  MECHANICAL    DENTISTRY. 

process  of  analysis  or  assaying,  they  should  always  be  made 
either  from  pure  gold  or  gold  coin,  the  standard  of  these  being 
definitely  fixed.  But  as  the  process  of  procuring  pure  gold  is 
somewhat  tedious  and  troublesome,  gold  coin  is  very  generally 
employed  for  the  purpose.  The  amount  of  alloy  necessary  to 
reduce  either  pure  or  coin  gold  to  any  particular  standard,  and 
the  method  of  ascertaining  the  carat  or  fineness  of  any  given 
alloy,  may  be  readily  determined  by  a  few  simple  rules.  The 
following  practical  remarks  on  the  method  are  taken  from  an 
article  on  "  Alloying  of  Gold,"*  by  Professor  G.  Watt. 

"  I.  To  Ascertain  the  Carat  of  any  given  Alloy. — The  pro- 
portion may  be  expressed  as  follows  : — 

"  As  the  weight  of  the  alloyed  mass  is  to  the  weight  of  gold 
it  contains,  so  is  24  to  the  standard  sought.  Take,  for  example, 
Harris's  No.  3  gold  solder  : — 

Pure  gold,  .......         6  parts. 

"     silver,  .......         2      " 

"     copper,         .......  I      " 

Total, 9 

"  The  total  proportion  would  be  expressed  thus  : — 

9   :   6   :  :   24   :    l6. 

"  From  this  any  one  can  deduce  the  following  : — 

"  Rule. — Multiply  24  by  the  weight  of  gold  in  the  alloyed 
mass,  and  divide  the  product  by  the  weight  of  the  mass  ;  the 
quotient  is  the  carat  sought. 

"  In  the  above  example,  24  multiplied  by  6,  the  quantity  of 
gold,  gives  144,  which,  divided  by  9,  the  weight  of  the  whole 
mass,  gives  16.  Hence,  an  alloy  prepared  as  above  is  16  carats 
fine. 

"As  another  example,  under  the  same  rule,  take  Harris's  No 
I  solder  : — 

22  carat  gold, 48  parts. 

silver,       .         .         .         .         .         .         .         16      " 

copper,     .  .  .  .  .  .  .  12       " 

Total, 76 

*  Dental  Register  of  ilie  West,  vol.  x,  p.  396. 


ALLOYS  OF  GOLD  FOR  DENTAL  PURPOSES.  95 

"  Now,  as  the  gold  used  is  but  22  carats  fine,  one-twelfth  of 
it  is  alloy.  The  one-twelfth  of  48  is  4,  which  subtracted  from 
48  leaves  44.     The  statement  then  is  : — 

76   :   44  ::   24   :    13.9. 

"This  solder,  therefore,  falls  a  fraction  below  14  carats. 

"  2.  To  Reduce  Gold  to  a  Required  Carat. — The  proportion 
may  be  expressed  as  follows  : — 

"  As  the  required  carat  is  to  24,  so  is  the  weight  of  the  gold 
used  to  the  weight  of  the  alloyed  mass  when  reduced.  The 
weight  of  gold  subtracted  from  this  gives  the  quantity  of  alloy 
to  be  added. 

"  For  example,  reduce  6  ounces  of  pure  gold  to  16  carats. 

"  The  statement  is  expressed  thus  : — 

16  :   24  :  :  6   :   9. 

"Six  subtracted  from  9  leaves  3,  which  is  the  quantity  of 
alloy  to  be  added.     From  this  is  deduced  the  following : — 

"  Rule. — Multiply  24  by  the  weight  of  pure  gold  used,  and 
divide  the  product  by  the  required  carat.  The  quotient  is  the 
weight  of  the  mass  when  reduced,  from  which  subtract  the 
weight  of  the  gold  used,  and  the  remainder  is  the  weight  of 
alloy  to  be  added. 

"  As  another  example  under  the  same  rule,  reduce  i  penny- 
weight of  22  carat  gold  to  18  carats. 

"  As  the  gold  is  only  22  carats  fine,  one-twelfth  of  it  is  already 
alloy.  The  i  pennyweight,  therefore,  contains  but  22  grains 
of  pure  gold.     The  statement  is,  therefore,  thus  expressed : — 

18  :   24  :  :   22   :   291^. 

"Twenty-two  subtracted  from  29^3  leaves  7^.  Therefore, 
each  pennyweight  of  22  carat  gold  requires  yy^  grains  of  alloy 
to  reduce  it  to  18  carats. 

"  3.  To  Raise  Gold  to  a  Higher  Carat. — This  may  be  done 
by  adding  pure  gold  or  a  gold  alloy  finer  than  that  required. 
The  principle  of  the  rule  may  be  set  forth  in  the  following 
general  expression : — 


96  MECHANICAL    DENTISTRY. 

"  As  the  alloy  in  the  required  carat  is  to  the  alloy  in  the  given 
carat,  so  is  the  weight  of  the  alloyed  gold  used  to  the  weight  of 
the  reduced  alloy  required.  The  principle  may  be  practically 
applied  by  the  following  : — 

"  Rule. — Multiply  the  weight  of  the  alloyed  gold  used  by  the 
number  representing  the  proportion  of  alloy  in  the  given  carat, 
and  divide  the  product  by  that  representing  the  proportion  of 
alloy  in  the  required  carat ;  the  quotient  is  the  weight  of  the 
mass  when  reduced  to  the  required  carat  by  adding  fine  gold. 

"  To  illustrate  this,  take  the  following  example: — 

"Raise  i  pennyweight  of  16  carat  gold  to  18  carats. 

"  The  numbers  representing  the  proportions  of  alloy  in  this 
example  are  found  by  respectively  subtracting  18  and  16  from 
24.     The  statement  is,  therefore — 


from  which  it  follows  that  to  raise  i  pennyweight  of  16  carat 
gold  to  18  carats,  there  must  be  one-third  of  a  pennyweight  of 
pure  gold  added  to  it. 

"  But  suppose  that,  instead  of  pure  gold,  we  wish  to  effect  the 
change  by  adding  22  carat  gold.  The  numbers,  then,  respect- 
ively representing  the  proportions  of  the  alloy  would  be  found 
by  subtracting,  in  the  above  example,  16  and  18  from  22,  and 
the  statement  would  be. 

4:6::    I    :    1^4. 

"  It  follows,  then,  that  to  each  pennyweight  of  16  carat  gold 
a  half  pennyweight  of  22  carat  gold  must  be  added  to  bring  it 
to  18  carats. 

"  By  the  above  rules,  we  think  the  student  will  be  able,  in  all 
cases,  to  calculate  the  fineness  or  quality  of  his  gold,  and  to 
effect  any  reduction,  whether  ascending  or  descending,  which  he 
may  desire." 


CHAPTER  VI. 

METHOD  OF  CONVERTING  GOLD  ALLOYS   INTO  THE  RE- 
QUIRED FORMS  FOR  DENTAL  PURPOSES. 

Manner  of  Procuring  an  Ingot. — The  gold  to  be  molded 
in  the  form  of  ingot  is  put  into  a  clean  crucible  lined  on  the 
inside  with  borax,  and  placed  in  the  furnace.  When  the  con- 
tained metals  are  perfectly  fused,  the  crucible  should  be  removed 
from  the  fire  with  a  pair  of  tongs,  and  the  contents  poured 
quickly  but  carefully  into  the  ingot  molds ;  the  latter  being 
placed  conveniently  near  the  mouth  of  the  furnace,  as  the  mol- 
tt:n   metals   soon  become  chilled  on  exposure  to  the  open  air. 

Fig.  49. 


Before  pouring,  the  moulds,  if  made  of  iron,  should  be  moder- 
ately heated  and  oiled,  or  coated  with  lamp  smoke  by  holding 
their  inner  surfaces  over  the  flame  of  an  oil  lamp  or  gas  jet. 

Ingot  molds  are  constructed  of  various  substances,  but  those 
in  most  common  use  are  formed  of  iron,  and,  for  gold,  are  gen- 
erally about  two  inches  square  and  from  one-eighth  to  one-sixth 
of  an  inch  thick  (Fig.  49).  They  should  be  slightly  concave 
on  their  inner  surfaces,  to  compensate  for  the  greater  shrinkage 
of  the  gold  in  the  center  than  at  the  margins  of  the  ingot. 
7  97 


98  MECHANICAL    DENTISTRY. 

Soapstone  is  sometimes  employed  for  the  same  purpose,  and 
is  preferred  by  some.  Molds  made  from  this  substance  should 
also  be  warmed  and  oiled  before  pouring  the  metals. 

Molds  are  also  made  from  charcoal,  which  is  highly  recom- 
mended for  the  purpose,  though  it  requires  to  be  frequently 
renewed.  Prof.  Gorgas,  in  commenting  on  the  relative  fitness 
or  value  of  the  several  substances  mentioned,  says  :  "  Iron  is 
perhaps  the  most  convenient ;  soapstone  gives,  with  the  same 
gold,  a  tougher  ingot;  whilst  with  charcoal,  the  greatest  tough- 
ness of  metal  is  obtained,  so  far  as  the  nature  of  the  ingot  mold 
can  modify  it.  Pig-iron,  from  the  same  furnace,  run  into  iron 
molds,  may  be  white  and  brittle  ;  or  into  sand  molds,  gray  and 
less  brittle;  or  into  charcoal,  dark  gray  and  soft.  Some  such 
molecular  arrangement  of  gold,  due  to  its  manner  of  cooling,  is 
probably  the  correct  explanation  of  the  fact  that  a  charcoal 
mold  yields,  other  things  being  equal,  a  tougher  ingot  than  iron." 

Charcoal  ingot  niolds  may  be  very  easily  and  quickly  made 
as  follows  :  Selecting  a  close-grained,  compact  piece,  of  suitable 
size,  cut  through  it  with  a  saw,  and  then  rub  the  divided  sur- 
faces together  until  perfect  coaptation  is  secured.  The  required 
size  and  shape  of  the  mold  is  then  cut  out  in  one  section  of  the 
block  ;  or  a  strip  of  sheet  iron,  a  little  broader  than  the  required 
thickness  of  the  ingot,  being  bent  into  proper  form,  is  placed 
between  the  two  pieces,  with  the  edges  partially  imbedded,  and 
the  whole  secured  in  place  by  binding  with  wire,  or  with  the 
use  of  clamps. 

Asbestos  Molds. — Comparatively  inexpensive,  and  at  the 
same  time  more  convenient  and  durable  contrivances  designed 
for  the  same  purpose,  combining  both  crucible  and  mold,  and 
embracing  the  special  advantages  claimed  for  charcoal,  may  be 
obtained  at  the  dental  depots.  One  of  the  simplest  forms  of 
this  kind  is  the  asbestos  melting  and  ingot  block  shown  in  Fig. 
50.  When  in  use,  place  a  piece  of  charcoal  over  the  bowl- 
shaped  portion  of  the  ingot  block,  as  it  facilitates  heating  the 
metal.  The  small  asbestos  slab  being  placed  m  position  to  com- 
plete the  mold,  and  retained  in  place  by  clamping,  the  metal, 
when  sufficiently  fused,  is  poured  into  the  mold  by  tipping  the 
block.     The  bowl  or  crucible  has  a  thin  coating  of  whiting,  to 


FORMING  GOLD  ALLOYS  FOR  DENTAL  USE. 


99 


prevent  borax  or  other  flux  from  adhering.  Should  this  occur, 
however,  rub  a  little  moist  whiting  in  the  bowl.  The  sides  of 
the  block  are  encased  in  strips  of  wood,  to  protect  the  hands 
from  heat. 

Carbon  Molds. — A  v^ery   ingenious,  convenient    and   useful 

Fig.  qo. 


apparatus,  combining  crucible  and  ingot  mold,  by  the  use  of 
which  ingots  of  gold,  silver,  etc.,  may  be  quickly  obtained  with- 
out the  use  of  a  furnace,  is  shown  in  Fig.  51.  The  crucible  is 
of  molded  carbon,  and  is  supported  in  position  by  an  iron  side- 

FiG.  51. 


plate.     A   clamp   holds   crucible   and    ingot   mold    in   position, 
swiveling  on  a  cast-iron  stand. 

The  metal  to  be  melted  is  placed  in  the  crucible,  and  the  flame 
of  the  blowpipe  directed  on  it  until  it  is  perfectly  fused.  The 
waste  heat  serves  to  make  the  ingot  mold  hot,  and  the  whole  is 


lOO 


MECHANICAL    DENTISTRY. 


tilted  over  by  means  of  the  upright  handle  at  the  back  of  the 
mold.  With  this  simple  instrument,  a  sound  ingot  may  be 
obtained  at  any  time  in  about  two  minutes. 

Aside  from  the  greater  convenience  and  cleanliness,  as  com- 
pared with  the  older  method  in  which  draft-furnace  heat  is  used, 
there  is  great  economy  of  time  in  the  use  of  the  last  named 
appliance  combining  crucible  and  mold,  since  an  ingot  may  be 
thus  obtained,  with  the  use  of  the  bellows  blowpipe,  in  from 
two  to  three  minutes.  It  is  suitable  for  melting  from  two  to 
four  ounces  of  gold  or  silver. 

It  not  infrequently  happens  that,  at  the  first  pouring,  the 
metals  arrange  themselves  in  the  ingot  in  accordance  with  the 


Fig.  52. 


Fig.  53. 


density  of  the  several  components,  those  of  greater  specific 
gravity  passing  to  the  bottom,  and  the  lighter  metals  remaining 
above.  Whenever  this  occurs,  the  ingot  must  be  broken  into 
pieces  and  remelted  ;  this  should  be  repeated,  if  necessary,  until 
the  alloy  assumes  a  perfectly  homogeneous  appearance.  It 
should  then  be  annealed  in  hot  ashes,  which  softens  the  gold 
and  removes  the  adhering  grease. 

Forging. — Before  laminating,  the  ingot  should  be  reduced 
somewhat  in  thickness  by  placing  it  on  an  even-faced  anvil  or 
other  equally  smooth  and  resistant  surface,  and  subjecting  it  to 
repeated  blows  with  a  tolerably  heavy  hammer.  It  should  be 
frequently  annealed,  and    the  process  of  forging  continued,  al- 


FORMING  GOLD  ALLOYS  FOR  DENTAL  USE. 


lOI 


ternately  hammering  and  annealing,  until  the  ingot  is  reduced 
one-half  or  more  in  thickness. 

Laminating  or  Rolling. — The  reduced  ingot,  well  annealed,  is 
next  laminated  or  spread  out  into  a  sheet  of  greater  or  less  thin- 
ness by  passing  it  repeatedly  between  two  strong,  highly-polished 
cylindrical  steel  rollers.  The  mills  used  for  the  purpose  are 
variously  constructed,  the    plainest    forms  (Fig.  52)  being  very 

Fig.  54. 


simple  in  their  mechanism,  while  others,  or  geared  mills,  are 
more  complicated,  and  are  constructed  with  a  view  to  a  greater 
augmentation  of  power,  and  precision  and  certainty  of  action. 
The  latter  (Figs.  53,  54),  if  of  approved  pattern,  materials,  and 
manufacture,  are,  upon  the  whole,  more  economical  and  reliable 
than  the  cheaper  varieties.  The  rollers,  for  the  purposes  of  the 
dentist,  should  be  from  three  to  four  inches  in  length. 


102  MECHANICAL    DENTISTRY. 

In  laminating,  the  rollers  should  first  be  adjusted  equidistant  at 
both  ends,  and  this  uniformity,  as  they  are  approximated  from  time 
to  time,  should  be  preserved  throughout.  At  every  passage  of 
the  gold  bar  between  the  rollers,  the  distance  between  the  latter 
should  be  diminished,  care  being  taken  that  the  approximation  be 
insufficient  to  clog  or  impede  the  free  action  of  the  mills.  The 
gold,  which,  in  time,  becomes  hard  and  brittle,  and  liable  to 
crack  in  the  mills,  should  be  frequently  and  well  annealed  by 
bringing  it  to  a  full  red  heat ;  this  restores  the  pliancy  of  the 
gold  and  facilitates  the  operation  in  the  press. 

When  the  ingot  has  been  extended  in  one  direction  as  far  as 
may  be  desired,  it  should  always  be  re-annealed  before  turning 
it  in  the  mills  ;  a  neglect  of  this  precaution  will  seriously  inter- 
fere with  the  working  of  the  gold  by  twisting  or  doubling  the 
plate  upon  itself;  and  in  some  instances,  provided  the  gold  has 
not  been  well  annealed  throughout  the  operation,  or  is  in  any 
considerable  degree  unmalleable,  the  plate  will  be  torn  across 
and  rendered  unfit  for  use. 

A  thin  or  retreating  edge  may  be  given  to  the  plate  at  any  de- 
sired point  or  points  by  passing  such  portions  part  way  between 
the  rollers  and  withdrawing;  repeating  this,  with  the  rollers 
brought  a  little  nearer  to  each  other  every  time  the  plate  is  in- 
troduced between  them,  and  decreasing  the  distance  the  plate 
passes  each  time  until  it  is  reduced  to  as  thin  an  edge  as  may  be 
desired. 

Standard  Gauge  Plate. — The  degree  of  attenuation  obtained 
by  rolling  is  determined  by  what  is  called  2i gauge  plate  (Fig.  55). 
This  instrument  is  usually  circular  or  oblong  in  form,  and  is 
marked  at  intervals  on  its  edge  by  cross-cut  grooves  or  fissures, 
which  successively  diminish  in  size  and  are  indexed  by  numbers 
ranging  from  5  to  36.  The  sizes  of  the  grooves  diminish  with 
the  ascending  numbers.  During  the  operation  of  rolling,  the 
plate  should  be  tested,  from  time  to  time,  by  the  gauge,  to  de- 
termine when  it  has  undergone  sufficient  attenuation. 

Thickness  of  Gold  Plate  required  as  a  Base  for  Artificial 
Dentures. — In  prescribing  the  thickness  of  plate  proper  for  the 
purpose  indicated,  no  estimate  can  be  given  that  will  apply  to  all 
cases,  as  certain  conditions  of  the  mouth,  to  be  mentioned  here- 


FORMING  GOLD  ALLOYS  FOR  DENTAL  USE. 


103 


after,  will  suggest  some  modifications  in  this  respect.  Usually, 
however,  plate  for  entire  upper  sets  should  correspond  in  thickness 
with  number  26  of  the  gauge  plate  ;  for  the  lozver  jaw,  nujnbcr  2^ 
may  be  used ;  while  for  partial  upper  pieces,  an  intermediate 
number  may  be  chosen,  unless  atmospheric-pressure  plates  are 
used,  when  the  number  recommended  for  full  upper  sets  maybe 
employed. 

Thickness  of  Plate  for  Clasps,  Stays,  etc.— Plate  for  these 
purposes  should  usually  correspond  with  number  22  of  the 
gauge  ;  a  less  amount  of  substance,  as  before  stated,  being  re- 
quired when  the  alloy  has  incorporated  with  it  a  small  propor- 
tion of  platinum.  . 

Fig.  55. 


Reduction  of  Gold  Solders  into  Proper  Form  for  Use. — 

The  method  of  converting  gold  solders  into  the  form  of  plate 
does  not  differ  from  that  already  described  in  the  manufacture 
of  plate  as  a  base,  except  that  when  zinc  or  brass  is  used,  the 
latter  should  be  added  after  the  other  constituents  are  completely 
fused,  and  then  instantly  poured,  to  prevent  undue  wasting  of 
the  base  metals  by  a  too  protracted  heat. 

The  solder  should  be  reduced  to  plate  somewhat  thinner  than 
that  used  for  upper  sets,  28  of  the  gauge  plate.  It  is  customary 
sometimes  to  roll  the  solder  into  very  thin  ribbons,  but  this  is 
objectionable  for  the  reason  that  a  greater  amount  of  the  alloy- 


I04 


MECHANICAL    DENTISTRY. 


ing  metals,  being  exposed  in  a  given  surface  to  the  action  of  the 
heat  in  soldering,  are  burnt  out  or  oxidated,  which  interrupts 
the  flow  and  weakens  the  attachment  between  the  solder  and 
plate. 

Method  of  Obtaining  Gold  Wire. — To  convert  gold  or  its 
alloys  into  the  form  of  wire,  the  operator  should  be  provided 
with  a  draw  plate,  a  vise,  and  a  pair  of  hand  pincers.  A  draw 
plate  (Fig.  56)  is  an  oblong  piece  of  steel  pierced  with  a  regular 
gradation  of  holes,  or  a  series  of  progressively  diminishing  aper- 
tures, through  which  the  gold  bar,  reduced  to  a  rod,  is  forced 
and   made   to    assume  the  form    and    dimensions  of  the    hole 

Fig.   56. 


through  which  it  is  last  drawn.  The  holes  are  formed  with  a 
steel  punch,  and  are  enlarged  on  the  side  where  the  wire  enters 
and  diminish  with  a  gradual  taper  to  the  other  side.  A  draiv 
bench  is  sometimes  employed  in  extending  the  wire,  the  power 
being  applied  by  a  toothed  wheel,  pinion,  and  rack-work,  and  is 
moved  by  the  hands  of  one  or  two  persons.  For  the  purposes 
of  the  dentist,  however,  it  will  be  sufficient  to  fix  the  draw  plate 
securely  between  the  jaws  of  a  bench  vise,  and,  by  seizing  hold 
of  one  end  of  the  gold  rod  with  a  strong  pair  of  clamps  or  hand 
pincers,  serrated  or  cut  like  a  file  on  the  inside  of  the  jaws,  the 
wire  may  be  drawn  steadily  through  the  plate,  passing  from  the 


FORMING  GOLD  ALLOYS  FOR  DENTAL  USE. 


105 


larger  to  the  smaller  holes  until  a  wire  of  the  required  size  is 
obtained. 

In  drawing  the  wire  the  motion  should  be  steady  and  uniform, 
for  if  drawn  interruptedly  or  by  jerks,  the  wire  will  be  marked 
by  corresponding  inequalities.  The  gold  rod  should  also  be 
annealed  from  time  to  time,  and  the  holes  kept  well  greased  or 
waxed. 

The  process  described  above  will  answer  equally  well  in 
reducing  any  of  the  ductile  metals  to  wire,  as  silver,  copper, 
platinum,, etc.,  so  that  any  further  description  of  the  method,  in 
connection  with  these  metals,  will  be  unnecessary. 

Fig.  57. 


Method  of  Constructing  Spiral  Springs. — Inasmuch  as 
spiral  springs  have  been,  to  a  great  extent,  superseded  by  more 
approved  agencies  employed  in  the  retention  of  artificial  teeth  in 
the  mouth,  and  as  all  the  principal  dental  furnishing  houses  are 
supplied  with  these  appliances  already  prepared  for  use,  it  does 
not  seem  necessary  to  enter  into  a  description  of  the  various 
apparatuses  used  in  making  them. 

The  following  simple  contrivance  will  meet  the  limited  require- 
ments of  those  who  are  obliged  or  prefer  to  manufacture  their 
own  springs.     The  wire,  obtained  as  already  described,  is  held 


I06  MECHANICAL    DENTISTRY. 

between  two  blocks  of  wood  fastened  between  the  jaws  of  a 
bench  vise,  as  shown  in  Fig.  57.  By  means  of  a  small  hand  vise, 
one  end  of  the  wire  is  clamped  to  a  uniformly  cylindrical  and 
well-tempered  steel  rod  or  wire,  four  or  six  inches  long,  and 
about  the  size  of  a  small  knitting-needle,  and  which  being  made 
to  revolve  while  resting  on  the  blocks  of  wood,  the  wire  is 
wound  firmly  and  compactly  around  it,  producing  a  uniform 
coil. 


CHAPTER  VII. 
SILVER. 

Ag  (Argentum). 

General  Properties  of  Silver. — Pure  silver,  when  planished, 
is  the  brightest  of  the  metals.  Fused,  or  in  the  form  of  ingot,  its 
specific  gravity  is  10.47  !  ^^^  when  hammered  or  condensed  in 
the  coining  press,  its  density  is  increased  and  its  specific 
gravity  becomes  10.6.  It  is  remarkably  laminable  and  ductile, 
yielding  leaves  not  more  than  ttoVoo  of  an  inch  thick,  and  wire 
400  feet  of  which  may  be  drawn  weighing  but  a  single  grain. 
It  exceeds  gold  in  tenacity  or  cohesion,  but  is  inferior  to  plati- 
num in  this  respect.  A  silver  wire  .078  of  an  inch  in  diameter 
will  sustain  a  weight  of  187.13  pounds.  Fine  silver  is  unaffected 
by  moisture  or  pure  atmospheric  air,  but  is  readily  tarnished 
with  a  film  of  brown  sulphuret  by  exposure  to  sulphuretted 
hydrogen.  The  sulphuret  of  silver  thus  formed  may  be  easily 
removed  by  rubbing  the  metal  with  a  solution  of  chameleon 
mineral,  prepared  by  calcining  equal  parts  of  black  or  peroxid 
of  manganese  and  nitre.  Unlike  gold  and  platimim^  it  is  readily 
soluble  in  nitric  acid,  this  and  sulphuric  acid  being  the  only  sim- 
ple ones  that  dissolve  it.  Silver  fuses  at  an  extreme  red  heat, 
generally  estimated  at  1873°  Fahrenheit.  It  becomes  very 
brilliant  when  heated  ;  boils  and  vaporizes  above  its  fusing  point ; 
and  when  cooled  slowly  its  surface  presents  a  crystalline  appear- 
ance. 

Alloys  of  Silver. — Silver  combines  readily  with  most  metals, 
forming  compounds  of  variable  degrees  of  malleability,  ductility, 
density,  etc. 

Tin,  zinc,  antimony,  lead,  bismuth,  and  arsenic  render  it  brittle. 
A  very  minute  quantity  of  tin  is  fatal  to  the  ductility  of  silver. 
Silver  does  not  easily  combine  with  iron,  although  the  two  metals 
may  be  united  by  fusion.  Gold,  copper,  platinum,  iridium,  steel, 
manganese,  and  mercury  also  form  alloys  with  silver. 

107 


I08  MECHANICAL    DENTISTRY. 

An  alloy  of  nine  parts  of  silver  and  one  part  of  copper  is  the 
Government  standard  of  the  United  States  coinage  since  1837. 
To  this,  three-cent  pieces  form  an  exception  ;  these  being  com- 
posed of  three  parts  silver  and  two  of  copper.  The  coins  of  silver 
having  a  greater  average  fineness  than  those  of  our  own  country 
are  Brazil,  Britain,  Chili,  France,  Greece,  Hindostan,  Persia, 
Portugal,  Rome,  and  Tuscany.  A  common  impression  prevails 
that  the  Mexican  silver  coin  contains  more  than  an  average  per- 
centage of  pure  silver,  and  it  is  therefore  sought  after  on  account 
of  its  supposed  purity.  This  is  true  of  some  pieces  coined  at 
different  periods,  but  the  average  fineness  of  the  Mexican,  as  well 
as  the  Spanish  coins,  falls  below  that  of  the  United  States  mints. 

Refining  Alloys  of  Silver. — The  following  accounts  of  the 
manner  of  obtaining  pure,  or  nearly  pure,  silver  from  alloys  of 
that  metal  by  the  dry,  and  wet  or  humid  methods,  are  given 
by  Prof  Essig  in  his  treatise  on  "  Dental  Metallurgy  :" — 

Dry  Method. — "  The  dry  method  or  assaying  process  con- 
sists in  forming  an  alloy  of  the  silver  with  lead,  and  is  especially 
applicable  to  ores  and  the  sweepings  of  the  dentist's  laboratory. 
The  specimen  to  be  treated  is  heated  with  from  twelve  to  thirty 
times  its  weight  of  granulated  lead,  in  a  bone-ash  cupel,  which 
is  placed  in  a  muffle  so  arranged  that  a  current  of  atmospheric 
air  may  pass  freely  over  the  vessel  and  oxidize  the  lead.  This 
oxid  of  lead,  being  quite  fusible,  combines  with  any  base  metal 
present  and  oxidizes  it,  uniting  subsequently  with  the  oxid  as 
a  fusible  slag,  while  the  gold  or  silver  will  be  held  by  the  unox- 
idized  portion  of  the  lead.  In  the  treatment  of  specimens  of 
alloy,  such  as  plate  or  coins,  a  quantity  of  the  specimen  is  ac- 
curately weighed  and  mixed  with  from  four  to  five  times  its 
weight  of  pure  granulated  lead.  It  is  then  placed  in  the  cupel 
and  exposed  to  heat,  as  above  described,  until  all  the  lead  is 
oxidized  or  converted  into  litharge,  when  the  remaining  button 
assumes  the  brilliant  appearance  of  surface  to  which  allusion 
has  been  previously  made,  denoting  that  the  base  metals  or 
oxidizable  constituents  have  been  oxidized  and  taken  up  by 
the  lead  oxid.  This  button  is  then  to  be  weighed  by  means 
of  a  delicate  assay  balance,  and  the  loss  of  weight  denotes  the 
amount  of  alloy  that  was  present. 


SILVER.  109 

Wet  Method. — "  Pure  silver,  which  is  reckoned  as  lOOO  fine, 
may  be  obtained  from  standard  or  other  grades  of  silver  by  dis- 
solving them  in  nitric  acid  slightly  diluted  with  water,  the  solution 
being  much  facilitated  by  exposure  to  gentle  heat.  If  gold  be 
associated  with  the  alloy  it  will  be  found  at  the  bottom  of  the 
vessel,  in  which  case  it  will  be  necessary  to  use  a  siphon  to  re- 
move the  argentic  nitrate  solution.  The  silver  is  now  to  be 
precipitated  in  the  form  of  chlorid  by  the  addition  of  an  excess 
of  common  salt.  When  all  has  subsided  the  liquid  is  carefully 
poured  off,  and  the  chlorid  thoroughly  washed,  to  remove  all 
traces  of  acid.  The  chlorid  is  then  placed  in  water  acidulated 
with  hydrochloric  acid  (an  ounce  of  chlorid  requiring  six  to 
eight  ounces  of  water)  and  pieces  of  clean  wrought-iron  put  in 
it,  when  a  copious  evolution  of  hydrogen  follows,  which,  uniting 
with  the  chlorin  of  the  argentic  chlorid,  liberates  metallic  silver. 
The  latter  should  not  be  disturbed  until  the  last  particle  of 
it  is  thus  reduced,  when  it  will  be  found  to  be  a  spongy  mass. 
The  undissolved  iron  should  now  be  carefully  removed,  the  fer- 
rous and  ferric  chlorid  carefully  decanted,  and  the  silver  washed 
in  hot  water  containing  about  one-tenth  its  bulk  of  hydrochloric 
acid.  This  is  repeated  several  times,  and  finally  the  silver  is 
again  thoroughly  washed  with  pure  hot  water.  The  silver,  after 
drying,  is  then  ready  for  melting,  and  if  care  has  been  observed 
in  the  process  it  will  be  found  to  be  of  a  fineness  of  999.7  parts 
in  1000,  the  0.3  of  impurity  present  being  due  to  traces  of  iron. 
The  chlorids  maybe  acidulated  with  sulphuric  acid,  and  reduced 
with  zinc  instead  of  iron. 

"  Another  method  of  precipitating  silver  in  the  metallic  form 
consists  in  placing  a  sheet  of  copper  in  a  solution  of  argentic 
nitrate.  The  metal  is  thrown  down  in  a  crystalline  form.  Silver 
thus  obtained  is  never  free  from  traces  of  copper. 

"  Pure  silver  can  only  be  obtained  from  samples  of  a  lower 
grade  by  fusing  the  pure  chlorid  with  sodium  carbonate.  The 
reaction  is  shown  in  the  following  equation  : — 

2AgCl  +  Na.COa  =  Ag,  -f  2NaCl  —  O  +  CO.. 

Owing  to  the  copious  evolution  of  carbonic  acid  gas  which  takes 
place   during    the   decomposition,  some   of  the  silver    may    be 


I  lO  MECHANICAL    DENTISTRY. 

thrown  from  the  crucible,  and  loss  may  occur  by  the  absorption 
by  the  crucible  of  some  of  the  fused  chlorid.  To  avoid  this, 
the  sides  of  the  vessel  should  be  coated  with  a  hot  saturated 
solution  of  borax. 

"  A  composition  of  lOO  parts  of  argentic  chlorid,  70.4  of 
calcic  carbonate  (chalk),  and  4.02  of  charcoal,  has  been  recom- 
mended as  a  means  of  obtaining  pure  silver.  This  mixture  is 
heated  to  dull  redness  for  thirty  minutes,  and  then  raised  to  full 
redness  ;  carbonic  acid  and  carbonic  oxid  are  given  off;  the 
calcic  chlorid  is  converted  into  calcic  oxychlorid,  underneath 
which,  in  the  bottom  of  the  crucible,  will  be  found  the  button 
of  pure  silver." 

Reduction  of  Silver  to  the  Required  Forms  for  Dental 
Purposes. — Owing  to  the  very  soft  and  flexible  nature  of  silver 
in  its  pure  state,  it  is  usual,  when  converting  it  into  plate  or 
other  forms  for  use,  to  employ  an  alloy  of  the  metal.  Hence 
silver  coins,  which  are  made  harder  by  the  copper  they  contain, 
are  generally  selected  for  the  purpose.  The  employment  of 
silver,  thus  debased,  as  a  base  for  dental  substitutes  is  regarded 
by  many  as  unsafe  and  injudicious.  Although  the  influences 
of  an  alloy  so  readily  acted  upon  as  this  by  the  various  agents 
which  affect  it  chemically  cannot  always  be  certainly  predicted 
in  every  case,  yet  no  reasonable  doubt  can  be  entertained  but 
that,  under  the  favoring  conditions  which  usually  exist  in  the 
mouth,  the  evils  accruing,  directly  and  indirectly,  to  the  organs 
of  the  mouth,  and  through  them  to  the  general  system,  are 
positive  and  undoubted.  If  used  at  all,  therefore,  it  should  be 
alloyed  with  the  least  practicable  amount  of  copper,  or,  what  is 
better,  pure  silver  should  be  reduced  with  platinum  alone,  in 
sufficient  quantities  to  impart  to  the  plate  an  adequate  degree 
of  strength  and  elasticity.  The  tendency  of  silver  to  tarnish  in 
the  mouth  when  alloyed  with  copper  may  be  diminished  by 
boiling  the  finished  piece  in  a  solution  of  cream  of  tartar  and 
chlorid  of  soda,  or  common  salt,  or  by  scrubbing  it  with  aqua 
ammonia,  which  removes  the  superficial  particles  of  copper 
and  exposes  a  surface  of  fine  silver.  When  platinum  is  intro- 
duced as  the  sole  alloying  component,  the  purity  of  the  silver 
is  not  only  preserved,  but  the  alloy  is  less  easily  acted  onchemi- 


SILVER.  I  I  I 

cally,  while  the  plate  derived  from  it  is  rendered  sufficiently 
inflexible  and  elastic.  From  three  to  five  grains  of  platinum 
may  be  added  to  one  pennyweight  of  pure  silver. 

On  account  of  the  strong  affinity  of  sulphur  for  silver,  the 
fuel  most  proper  to  be  used  in  melting  it  is  charcoal.  The  vari- 
ous processes  employed  in  the  conversion  of  silver  into  the 
required  forms  for  use  are  similar  to  those  described  for  gold, 
and  need  not  be  recapitulated. 

Formulas  for  Silver  Solders. — Silver  solders  are  usually 
composed  of  silver,  copper,  and  zinc  in  variable  proportions. 
Alloys  formed  from  the  following  formulas  are  such  as  are  gen- 
erally employed  in  soldering  silver  plate  derived  from  the  coins 
of  that  metal.  Three-cent  pieces,  composed  of  two  parts  silver 
and  one  of  copper,  may  be  used  for  the  same  purpose  : — 

Foifnula  No.  I.  Formula  N^o.  2. 

Silver, 66  parts.  Silver 6  parts. 

Copper,    ....  30     "  Copper, 2     " 

Zinc, 10     "  Brass, i  part. 

When  the  material  to  be  united  is  composed  of  pure  silver 
and  platinum,  silver  coin  alloyed  with  one-tenth  zinc  may  be 
used  as  a  solder. 

In  compounding  silver  solders,  the  silver  and  copper  should 
be  first  melted,  and  the  zinc  or  brass  afterward  added,  when 
they  should  be  quickly  poured,  to  prevent  undue  waste  by 
oxidation  of  the  more  fusible  component.  The  ingot,  when 
cold,  should  be  rolled  into  a  plate  a  little  thicker  than  that 
recommended  for  eold  solder. 


CHAPTER  VIII. 

PLATINUM. 
Pt. 

General  Properties. — Platinum  is  a  grayish-white  metal,  re- 
sembling, in  some  measure,  polished  steel.  It  is  harder  than 
silver,  and  has  a  density  greater  than  any  other  known  metal, 
its  specific  gravity  being  21.25.  It  remains  unaltered  in  the 
highest  heat  of  a  smith's  forge,  and  can  only  be  fused  by  means 
of  the  oxy-hydrogen  blowpipe  and  galvanism.  A  white  heat 
does  not  tarnish  it,  nor  is  it  in  any  way  affected  by  exposure,  either 
in  the  air  or  water.  It  is  insoluble  in  any  of  the  simple  acids ; 
nitro-miiriatic  acid  (aqua  regia)  being  the  only  one  that  dissolves  it. 
It  is  sufficiently  malleable  to  be  hammered  into  leaves  so  thin 
as  to  be  blown  about  by  the  breath.  It  may  be  drawn  into 
wire  two-thousandths  of  an  inch  in  diameter,  and  a  still  greater 
attenuation  may  be  obtained  by  coating  the  wire  with  silver, 
drawing  it  out,  and  dissolving  off  the' latter  metal.  It  expands 
less  by  heat  than  any  other  metal,  and  is  much  inferior  to  gold, 
silver,  and  copper  as  a  conductor  of  electricity.  While  it  does 
not  oxidize  in  the  air  at  any  temperature,  nor  is  soluble  in  any 
one  acid,  if  heated  to  redness  in  the  air,  in  contact  with  caustic 
alkalies  or  alkaline  earths,  a  hydrated  oxid  is  formed  which 
combines  with  the  alkaline  base  in  a  similar  manner  to  palladium. 

Platinum  is  very  soft  and  flexible,  and  when  rolled  into  thin 
sheets,  say  28  or  30  of  the  gauge-plate,  and  well  annealed  at  a 
strong  tvhite  heat  for  eight  or  ten  niin?ttes,  it  may  be  readily  forced 
into  all  the  inequalities  of  a  zinc  die  without  producing  any 
appreciable  change  in  the  face  of  the  latter. 

The  Fusing  Point  of  platinum  is  above  3500°  Fahrenheit,  to 
reach  which,  in  the  laboratory,  it  is  necessary  to  employ  the 
oxy-hydrogen  blowpipe. 

The  following  interesting  and  practical  observations  on  the 
method   of  melting  platinum    scraps  are   by  E.  A.  L.  Roberts. 

1 12 


PLATINUM.  113 

By  the  process  of  welding,  the  operator  will  be  enabled  to  re-con- 
vert his  waste  scraps  of  platinum  into  convenient  forms  tor  use, 
and  of  which  he  could  not  otherwise  avail  himself,  on  account  of 
the  infusible  nature  of  this  metal  in  its  uncombined  state  : — 

"  Platinum  used  by  dentists  should  be  soft,  tough,  and  with- 
out flaws.  These  qualities  can  be  attained  only  by  thorough 
melting  and  welding.  The  welding  must  be  done  at  a  white 
heat.  When  the  surface  is  cool  enough  to  be  visible,  the  metal 
is  too  cool  to  be  welded,  and  every  blow  is  injurious,  because  it 
has  a  tendency  to  shatter  and  shake  it  to  pieces.  The  necessary 
delicacy  of  this  process  and  the  uncertainty  of  success  has  led 
some  writers  to  declare  that  platinum  is  incapable  of  being 
welded.  The  platinum  must  be  perfectly  clean,  and  must  be 
heated  in  a  muffle.  When  welded,  the  metal  should  be  handled 
with  tongs  plated  with  platinum,  and  hammered  with  a  clean 
hammer  on  a  clean  anvil,  both  of  which  should  be  as  hot  as 
possible  without  drawing  the  temper  of  the  steel.  The  hammer 
used  in  welding  should  weigh  about  a  pound,  to  prevent  drawing 
the  metal ;  but  when  welded  the  metal  may  be  forged  with  a 
heavier  hammer. 

"  The  scraps  or  sponge  should  be  condensed  in  a  square  mold, 
very  compactly,  two  pieces  of  which,  weighing  from  ten  to 
twenty  ounces,  may  be  put  in  a  muffle  together.  When  the 
heat  becomes  so  great  that  on  opening  the  door  the  metal  be- 
comes invisible,  bring  one  of  the  pieces,  in  the  tongs,  quickly  to 
the  anvil,  give  it  three  or  four  quick,  sharp  blows,  in  rapid  suc- 
cession. Return  the  piece  to  the  muffle,  and  proceed  with  the 
other  piece  in  like  manner,  and  thus  alternately  until  both  are 
thoroughly  welded. 

"  Platinum  should  never  be  thrown  into  water  while  hot,  as 
that  tends  to  make  it  crystallize.  It  should  be  thoroughly 
hammered,  which  makes  it  tough  and  fibrous. 

"  The  following  process  gives  the  best  results  in  melting  this 
metal.  Condense  the  scraps,  sponge,  or  filings  in  an  iron  mold. 
Lay  the  condensed  mass  on  a  concave  fire-brick,  and  heat  it  to 
whiteness.  Take  the  brick  from  the  muffle,  and  place  it  in  a 
sheet-iron  pan,  coated  with  plaster  and  asbestos.  The  pan 
should  be  deep  enough  and  broad  enough  to  catch  all  globules 


I  14  MECHANICAL    DENTISTRY. 

and  other  loose  particles  of  the  metal.  Place  it  under  the  jet  of 
the  oxy-hydrogen  blowpipe  in  the  following  manner : — 

"  The  pan  is  provided  with  a  handle,  opposite  to  which  is  a 
ring,  which  is  to  be  attached  to  an  iron  hook  and  rod,  suspended 
from  the  ceiling  by  a  slip  of  india-rubber,  which  enables  the 
operator  to  hold  the  pan  conveniently  at  any  distance  from  the 
jet  of  the  burning  gases.  The  hydrogen  is  first  lighted,  and 
gives  a  powerful  flame,  but  as  the  oxygen  combines  with  it,  the 
flame  subsides  into  an  intense  focus  of  heat,  in  which  the  metal 
is  soon  brought  to  a  state  of  fusion.  Begin  at  one  end  and  melt 
along  toward  the  other,  till  the  whole  is  fused  in  one  mass. 
The  platinum  in  this  condition,  when  cool,  is  quite  crystallized 
and  sonorous.  It  breaks  very  easily,  like  spelter-zinc.  Heat  it 
very  hot  and  forge  it.  A  continuation  of  this  process  renders  it 
soft,  tough,  and  fibrous.  When  reduced  to  the  width  desired, 
and  to  the  thickness  of  one-fourth  of  an  inch,  it  should  be  made 
very  hot  and  passed  instantly  through  the  rollers." 

Use  for  Dental  Purposes. — Platinum,  in  mechanical  prac- 
tice, is  chiefly  employed  as  a  base  for  continuous-gum  work ; 
as  a  coloring  ingredient  of  porcelain ;  for  pins  for  attaching 
mineral  teeth  ;  for  backings,  and  dowels  in  crown-  and  bridge- 
work  ;  and,  to  a  limited  extent,  in  some  of  the  minor  operations 
of  the  shop. 

Solder  for  Platinum. — Pure  gold  is  the  only  proper  solder 
for  this  metal. 

Alloys  of  Platinum. — Platinum  unites  with  most  of  the  base 
metals,  forming  alloys  of  variable  degrees  of  hardness,  elasticity, 
brittleness,  color,  fusibility,  etc.,  but  their  practical  value  to  the 
dentist  is  not  sufficient  to  justify  a  separate  description  of  their 
properties. 

Alloyed  with  gold  it  forms  a  straw-colored  alloy,  the  shade 
depending  on  the  quantity  of  gold  added.  Silver  hardens  it,  the 
resulting  alloy  being  unaffected  by  sulphur. 

Platinoid  Metals. — The  platinoid  metals,  palladium,  iridium, 
osmium,  rhodium,  and  ruthenium,  are  native  contaminations,  the 
alloys  of  these  metals  having  a  close  general  resemblance  to 
platinum. 

Among  the  platinoid  metals,  palladium  and  iridium  are  the 


PLATINUM.  115 

only  ones  that  have  been  used  for  dental  purposes,  and  these 
only  to  a  limited  extent.  Palladium  is  of  a  steel-gray  color,  and 
when  planished,  is  a  brilliant  steel-white  metal,  not  liable  to 
tarnish  in  the  air.  Though  closely  resembling  platinum,  it  may 
be  readily  distinguished  from  the  latter  metal  by  the  following 
tests  :  I.  It  has  little  more  than  one-half  the  density  of  platinum. 
2.  If  a  piece  of  it  is  heated  to  redness,  it  assumes  a  bronze-blue 
shade,  of  greater  or  less  intensity,  as  it  is  cooled  more  or  less 
slowly  ;  but  if  it  is  suddenly  chilled  by  immersing  it  in  cold  water, 
it  instantly  resumes  its  original  luster.  3.  When  a  drop  of  the 
tincture  of  iodin  is  let  fall  upon  its  surface  and  evaporated  over 
the  flame  of  a  lamp,  a  black  spot  remains,  which  does  not  occur 
with  platinum.  Palladium  melts  at  about  the  heat  required  to 
fuse  malleable  iron,  and  is  the  most  fusible  of  the  platinoid 
metals.  It  is  soluble  in  nitric  acid,  but  its  best  solvent  is  nitro- 
hydrochloric  acid. 

Palladium,  being  very  costly,  and  possessing  no  properties  that 
specially  recommend  it  for  dental  use,  is  but  little  employed  in 
prosthetic  practice. 

Iridium,  though  generally  found  associated  with  platinum, 
osmium,  and  other  allied  metals,  sometimes  occurs  native  and 
nearly  pure.  Like  platinum,  it  is  very  refractory  when  exposed 
to  high  temperatures,  and  can  only  be  fused  by  the  oxy-hydro- 
gen  blowpipe  or  by  the  heat  of  the  voltaic  current.  An  alloy 
of  one-fifth  platinum  and  four-fifths  iridium  has  been  met  with 
in  octahedral  crystals,  whiter  than  platinum,  and  of  specific 
gravity  22.66.  When  native  platinum  is  dissolved  in  nitro-hy- 
drochloric  acid,  black  scales  remain  behind,  which  are  composed 
of  iridium  and  osmium.  These  metals  may  then  be  separated  by 
one  of  the  methods  in  use,  and  the  iridium  is  obtained  in  a  gray 
metallic  powder,  resembling  spongy  platinum.  Iridium  is  very 
hard,  white,  and  brittle,  and  has  a  specific  gravity  of  21.15. 
None  of  the  acids  attack  the  pure  metal,  but  when  alloyed  with 
platinum  it  is  readily  dissolved  by  aqua  regia  or  nitro-hydro- 
chloric  acid.  If  heated  in  a  finely  divided  state  in  the  open  air, 
iridium  absorbs  oxygen  ;  it  is  also  oxidized  by  niter  and  caustic 
potash. 

The  extreme  hardness    and    consequent    rigidity   of  iridium 


Il6  MECHANICAL    DENTISTRY. 

renders  it,  in  its  unalloyed  state,  practically  unfit  for  base  plates 
on  account  of  the  great  difficulty  of  swaging  it  into  proper  form. 
This,  however,  may  be  accomplished  in  certain  cases,  as  in  par- 
tial pieces,  with  the  use  of  zinc  dies  and  counters  ;  and  ;n  these 
cases  it  is  desirable  on  account  of  the  increased  strength  its 
property  of  hardness  imparts  to  the  plate.  It  may  be  used  to 
advantage,  however,  alloyed  with  platinum,  a  small  quantity 
imparting  to  the  latter  increased  stiffness  and  elasticity. 


CHAPTER  IX. 

ALUMINUM. 

Al. 

Derivation. — Aluminum  is  the  metallic  basis  of  alumina,  the 
latter  being  the  characteristic  ingredient  of  common  clay.  It  is 
only  within  the  past  few  years  that  the  attention  of  chemists  has 
been  directed  to  the  production  of  this  remarkable  metal,  with  a 
view  to  its  general  introduction  into  commerce  and  the  arts. 
Prior  to  the  researches  of  M.  Deville,  who,  under  the  patronage 
of  the  then  Emperor  of  the  French,  commenced  his  researches 
in  1854  for  the  production  of  this  metal  on  a  large  scale,  the 
small  quantities  produced,  and  the  corresponding  exorbitant  prices 
it  commanded,  rendered  it  entirely  unavailable  for  other  purposes 
than  merely  scientific  experiment.  The  improvements  in  the 
methods  of  obtaining  it,  however,  which  have  been  more  re- 
cently introduced,  have  rendered  its  production  more  economical, 
and  it  is  now  supplied  in  much  larger  quantities,  and  at  a 
corresponding  reduction  in  the  cost  of  the  metal. 

The  following  account  of  the  properties  of  this  metal  is  taken 
from  a  paper  read  before  the  Society  of  Arts,  London,  by  its 
secretary,  P  Le  Neve  Foster.  It  embodies  a  very  complete  de- 
scription of  the  properties  of  this  remarkable  metal : — 

General  Properties. — "  One  of  the  most  striking  properties  of 
aluminum  is  its  extreme  lightness,  its  specific  gravity  being  2.6, 
nearly  that  of  glass,  whilst  that  of  platinum  is  21.5,  gold  19.5, 
copper  8.96,  zinc  7.2,  tin  7.3. 

"  The  metal  is  malleable,  ductile,  almost  without  limit ;  it  can 
be  reduced  to  very  thin  sheets  or  drawn  into  very  fine  threads. 
Its  tenacity,  though  superior  to  that  of  silver,  is  less  than  that  of 
copper;  but  no  very  accurate  experiments  have  been  made  in 
this  respect. 

"  When  pure  it  is  about  as  hard  as  sil\-er.  Its  elasticity  is  not 
great.     It  files  readily,  and  is  said  not  to  injure  the  file.     It  con- 

117 


Il8  MECHANICAL    DENTISTRY. 

ducts  electricity  with  great  facility,  so  that  it  may  be  considered 
as  one  of  the  best  conductors  known,  almost  equal  in  this  respect 
to  silver,  and  more  than  eight  times  a  better  conductor  than  iron. 
It  melts  at  a  temperature  a  little  above  that  of  zinc,  between  zinc 
and  silver.  In  its  chemical  qualities  it  would  seem  to  take  an 
intermediate  rank  between  what  are  termed  the  noble  metals  and 
the  common  metals,  being,  as  Deville  states,  one  of  the  most 
unalterable  of  metals. 

"  It  might  be  imagined  that  it  would  as  readily  reassume  its 
oxygen  as  it  parted  with  it  with  difficulty  when  in  its  state  of 
oxid.  This,  however,  is  not  the  case  ;  it  appears  to  be  as  indif- 
ferent to  oxygen  as  either  platinum  or  gold.  In  air  and  in  oxy- 
gen it  undergoes  no  sensible  alteration,  and  it  even  resists  it  at 
the  highest  temperature  which  Deville  could  produce  in  a  cupel- 
ling furnace,  a  temperature  higher  than  that  employed  in  assaying 
gold.  Water  has  no  action,  according  to  Deville,  on  aluminum, 
neither  at  its  ordinary  temperature,  nor  when  boiling,  nor  even 
upon  the  metal  at  a  low,  red  heat,  near  its  melting  point. 
According  to  Professor  Grace  Calvert,  this  statement  must  be 
received  with  some  degree  of  caution,  as  in  experiments  he  has 
made  he  considers  that  oxidation  does  take  place  slowly  when 
the  metal  is  immersed  in  water  for  any  considerable  length  of 
time.  It  is  not  affected  by  sulphur  or  sulphureted  hydrogen, 
like  silver,  nor  is  it  acted  upon  to  any  considerable  degree  by 
any  of  the  oxy-acids  in  the  cold ;  nitric  acid,  whether  strong  or 
weak,  at  its  ordinary  temperature  in  no  way  afTects  it,  though 
when  boiUng  it  acts  upon  it  slowly.  Small  grains  of  aluminum, 
plunged  in  sulphuric  acid  for  three  months,  remained  apparently 
unaltered.  The  vegetable  acids,  such  as  acetic,  oxalic,  and  tar- 
taric acids,  have  scarcely  any  effect  on  it  at  all.  The  true  solvent 
of  the  metal  is  hydrochloric  acid,  which  attacks  it  rapidly.  It 
appears  to  resemble  tin  when  brought  into  contact  with  hydro- 
chloric acid  and  the  chlorids.  Its  absolute  harmlessness  permits 
of  its  being  employed  in  a  vast  number  of  cases  where  the  use 
of  tin  would  not  be  desirable  on  account  of  the  extreme  facility 
with  which  that  metal  is  dissolved  in  the  organic  acids. 

"  Figuier,  in  his  scientific  Year  Book,  states   that   the  caustic 
alkalies,  potash,  and  soda,  and  even  ammonia,  dissolve  aluminum 


ALUMINUM.  119 

sensibly.  He  also  states  that  common  salt  and  acetic  acid 
(vinegar),  especially  when  mixed,  attack  and  dissolve  aluminum. 
He  adds,  that  the  mixture  of  salt  and  vinegar  for  seasoning  a 
salad,  made  in  a  spoon  of  aluminum,  feebly  but  inevitably 
attacks  it. 

"All  these  points,  however,  deserve  to  be  inquired  into,  as 
there  seems  some  discrepancy  between  different  writers  on  them." 

Alloys. — "  Aluminum,  like  iron,  does  not  unite  with  mercury, 
and  scarcely  at  all  with  lead.  It,  however,  forms  a  variety  of 
alloys  with  other  metals.  It  can  be  alloyed  with  iron,  and  when 
aluminum  becomes  cheaper  it  will  be  curious  to  see  what  effect 
mixtures  of  this  metal  with  iron  will  have  upon  its  quality, 
whether  for  good  or  for  evil.  It  seems  to  unite  readily  with  zinc, 
and  these  have  been  found  to  give  the  best  promise  as  solders  for 
aluminum;  but,  unfortunately,  when  melted,  neither  of  them  are 
sufficiently  liquid,  and  do  not  run  readily.  The  joints  will  not 
bear  a  blow.  A  variety  of  alloys  with  nickel  have  been  made, 
and  that  consisting  of  100  parts  of  aluminum  and  3  of  nickel  is 
found  to  work  readily,  and  to  have  gained  hardness  and  rigidity, 
as  compared  with  the  pure  metal.  The  alloys,  however,  with 
copper  are  the  most  striking;  they  are  light  and  very  hard,  and 
capable  of  a  fine  polish.  In  the  same  degree  that  copper  adds  to 
the  hardness  of  aluminum,  so  does  the  latter,  when  used  in  small 
quantities,  give  hardness  to  copper,  without,  however,  injuring  its 
malleability.  It  renders  it  susceptible  of  a  fine  polish,  and,  ac- 
cording as  the  proportions  are  varied,  the  color  of  the  alloy  be- 
comes deep  or  pale  gold.  Alloys  of  copper  with  five  and  ten  per 
cent,  of  aluminum  resemble  gold,  perhaps,  more  than  any  other 
metallic  alloy  hitherto  enjployed.  They  do  not  tarnish  sensibly 
by  exposure  to  the  air.  Aluminum  can  be  deposited  by  the  bat- 
tery, and  by  the  same  agent  it  can  be  gilt  or  silvered." 

Dental  Uses. — For  several  years  past  attempts  have  been 
made  to  render  aluminum  available  as  a  base  for  artificial  den- 
tures,both  bythe  swaging  and  casting  processes,  with  only  partial 
success.  When  in  the  form  of  plate  no  suitable  solder  has  yet 
been  discovered  by  which  the  several  parts  of  a  dental  appliance 
may  be  securely  united,  and  experiments  in  casting  have  not  yet 
proven  entirely  satisfactory.     It  is  being  used  to  a  limited  extent, 


I20  MECHANICAL    DENTISTRY. 

with  rubber  attachment,  and  it  is  hoped  that  in  the  near  future, 
upon  further  acquaintance  with  its  capabilities,  it  may  prove  en- 
tirely acceptable  for  dental  purposes. 

At  the  present  time  its  use  is  rarely  attempted,  except  as  a 
base  in  connection  with  rubber  or  celluloid,  the  latter  substances 
being  employed  as  a  means  of  attaching  teeth  by  a  method 
similar  to  that  described  in  another  place  when  gold  or  silver 
plate  is  used. 


CHAPTER  X. 
COPPER,  ZINC,  LEAD,  TIN,  ANTIMONY,  AND  BISMUTH. 

COPPER. 
Cu  (Cuprum). 

General  Properties. — Copper  is  one  of  the  metals  most 
anciently  known  ;  it  is  of  a  brownish-red  color,  with  a  tinge  of 
yellow  ;  has  a  faint  but  nauseous  and  disagreeable  taste,  and  im- 
parts, when  exposed  to  friction,  a  smell  somewhat  similar  to  its 
taste.  Its  specific  gravity  ranges  from  8  8  to  8.9.  It  is  both 
malleable  and  ductile,  but  excels  in  the  former  property,  finer 
leaves  being  obtained  from  it  than  wire.  It  is  inferior  to  iron  in 
tenacity,  but  surpasses  gold,  silver,  and  platinum  in  this  respect. 
The  Fusing  Point  of  copper  is  about  2000°  Fahrenheit. 

Alloys  of  Copper. — Copper  unites  readily  with  most  metals, 
forming  alloys  of  great  practical  value  in  the  arts,  but  which  have 
but  a  limited  application  in  dental  laboratory  processes.  Many 
of  these  alloys  are  curious  and  instructive,  as  illustrating  the 
singular  and  unaccountable  influence  of  alloying  upon  the  dis- 
tinctive properties  of  the  component  metals.  Copper  and  tin,  for 
example — the  former  of  which  is  highly  ductile,  and  the  latter 
equally  malleable — when  combined  in  the  proportion  to  form 
speculum  metal  (9  C  :  i  T),  form  an  alloy  distinguished  for  its  ex- 
treme brittleness,  with  a  surface  hardness  almost  equal  to  steel. 
By  increasing  the  quantity  of  tin  until  the  compound  assumes 
the  proportions  constituting  gun-metal  (C  2  :  T  i),  the  alloy, 
though  neither  malleable  nor  ductile,  becomes  eminently 
tough  and  rigid.  Other  prom^inent  examples  might  be  given, 
showing  how  completely  this  combining  influence  defies  all  cal- 
culations in  regard  to  ultimate  results.  The  following  summary 
embraces  the  names  and  composition  of  the  more  familiar  alloys 
of  copper,  omitting,  as  unnecessary  in  this  connection,  a  descrip- 
tion of  their  individual  properties. 

121 


122  MECHANICAL    DENTISTRY. 

Alloys  of  Copper  with  Zinc. — Brass  is  an  alloy  of  uncertain 
and  variable  composition,  consisting  usually,  however,  of  two  to 
five  pa rts^ of  copper  and  one  of  zinc.  Brass  melts  at  1869°  Fahr. 
Prmce's  metal,  and  its  allied  compounds,  PincJibeck,  Siviilor,  and 
Manheim  gold,  consists  of  nearly  equal  parts  of  copper  and  zinc. 
Mosaic  gold  consists  of  100  parts  of  copper  and  from  52  to  55  of 
zinc.  Dutch  gold,  ^vom  which  foil  of  that  name  was  formerly  ob- 
tained, is  formed  of  1 1  parts  of  copper  with  2  of  zinc.  Baih  metal 
is  composed  of  32  parts  of  brass  and  9  of  zinc. 

Brass  Solder  consists  of  two  parts  of  brass  and  one  of  zinc, 
to  which  a  little  tin  is  occasionally  added. 

Alloys  of  Copper  with  Tin. — Bell  metal  usually  consists  of 
100  parts  of  copper  with  from  60  to  63  parts  of  tin.  Cannon 
metal  is  compounded  of  90  parts  of  copper  with  10  of  tin. 
Cymbals  and  gongs  contain  100  parts  of  copper  and  25  of  tin. 
Specuhim  metal  consists  of  two  parts  of  copper  and  one  of  tin. 

Copper  and  arsenic  form  a  white-colored  alloy,  which,  in  the 
proportion  of  nine  parts  of  copper  and  one  of  arsenic,  is  white, 
slightly  ductile,  and  is  denser  and  more  fusible  than  copper 

German  Silver  is  composed  of  copper,  40.4;  nickel,  31.6; 
zinc,  25.4;  iron,  2.6;  but  the  proportions  of  the  metals  of  this 
alloy  differ  according  to  the  various  uses  to  which  this  com- 
pound is  applied. 

Babbitt  metal  is  a  compound  of  copper,  antimony,  and  tin, 
in  somewhat  varying  proportions.  The  following  formula  is 
given  by  Henry  Long  Jacob  in  the  British  Journal  of  Dental 
Science : — 

Copper,      2  parts 

Antimony, 3  P^rts 

Tin, 12  parts 

The  following  method  of  preparing  it  is  given  by  the  same 
writer  : — 

"  In  preparing  this  metal,  the  copper  is  first  melted  in  a 
crucible,  with  about  an  equal  weight  of  tin  (the  copper  thus 
fusing  much  more  readily  than  by  itself);  a  little  more  of  the 
tin  is  then  added,  next  the  antimony,  and  lastly  the  remainder 
of  the  tin  by  degrees,  stirring  well  during  the  whole  of  the  time; 
the   metal   can  then   be   poured   into   sand  molds   of  any   con- 


ZINC.  123 

v^enient  form.  About  a  year  and  a  half  ago  I  furnished  Mr, 
Thomas  Fletcher  with  this  formula,  and  I  believe  it  is  given  in 
his  work  on  '  Dental  Metallurgy.'  The  melting  point  of  this 
metal  is  lower  than  that  of  zinc  and  somewhat  higher  than 
that  of  lead,  so  that  counter-molds  of  this  latter  can  be  readily 
made  to  it  with  proper  care.  I  am  under  the  impression  that 
the  original  Babbitt  metal  was  said  to  contain  a  portion  of  lead, 
but  this  addition  was  found  to  be  injurious.". 


ZINC. 

Zn  (Zincum). 

General  Properties. — Zinc  is  a  bluish-white  metal,  possess- 
ing considerable  luster  when  broken  across.  The  commercial 
variety  is  always  impure,  containing  traces  of  iron,  lead,  cad- 
mium, arsenic,  carbon,  etc.  It  does  not  easily  tarnish  in  dry 
air,  but  soon  becomes  dull  on  exposure  to  moisture.  In  the 
condition  in  which  it  ordinarily  occurs  it  is  a  brittle  metal,  but 
may  be  rendered  malleable  by  annealing  it  at  certain  tempera- 
tures. This  change  in  its  condition  is  effected  by  subjecting  it 
to  a  heat  of  from  220°  to  300°  F.,  at  which  temperature  it  may 
be  rolled  into  sheets,  and  retain  its  malleability  when  cold.  The 
best  annealing  temperature  for  zinc  is  about  245°  F.  A  knowl- 
edge of  this  fact  will  enable  the  operator  to  avail  himself  of  the 
advantages  of  this  property  by  annealing  his  zinc  die,  by  which 
its  liability  to  crack  or  part  under  the  hammer  is  diminished. 

The  Fusing  Point  of  zinc  is  about  775°  F.,  and  when  heated 
much  above  this  point  with  contact  of  air,  it  burns  with  a 
brilliant,  greenish-white  flame,  while  woolly-looking  flocculi 
rise  from  the  vessel  in  which  it  is  being  heated  and  float  in  the 
air.     The  specific  gravity  of  zinc  varies  from  6.9  to  7.2. 

Use  for  Dental  Purposes. — Zinc  has  been  long  and  almost 
exclusively  employed  in  the  formation  of  dies  used  in  swaging 
metallic  plates  employed  in  mounting  artificial  teeth,  and  experi- 
ence has  very  justly  accorded  to  it  undisputed  pre-eminence 
above  all  other  unalloyed  metals  for  the  purpose.  A  more 
particular  account  of  its  peculiar  fitness  for  dental  purposes  will 
be  given  under  the  head  of  Metallic  Dies  and  Counter-Dies. 


124  MECHANICAL    DENTISTRY. 

LEAD. 

Pb  (Plumbum). 

Properties. — Lead  has  a  grayish-blue  color,  with  a  bright 
metallic  luster  when  melted  or  newly  cut,  but  it  soon  becomes 
tarnished  and  dull-colored  when  exposed  to  the  air.  The 
specific  gravity  of  commercial  lead,  which  is  usually  contam- 
inated with  other  metals,  is  11.352. 

The  Fusing  Point  of  lead  is  617°  F.  Exposed  to  a  high 
heat,  it  absorbs  oxygen  rapidly,  forming  on  its  surface  a  gray 
film  of  protoxid  and  metallic  lead.  It  is  both  malleable  and 
ductile,  but  soft  and  perfectly  inelastic. 

Its  Use  in  the  Laboratory. — Lead,  either  in  its  pure  state  or 
when  alloyed  with  certain  other  metals,  serves  important  pur- 
poses in  the  dental  laboratory.  In  its  simple  or  uncombined 
state  it  is  useful  only  in  forming  counter-dies.  Alloyed  with 
antimony  in  the  proportion  of  ^  to  )^  of  the  latter,  with  the 
addition  sometimes  of  very  small  portions  of  copper,  tin,  and 
bismuth,  it  forms  different  grades  of  type-metal,  which  is  harder 
than  lead  and  very  brittle,  and  is  sometimes  used  for  dies  ;  and 
sometimes,  though  very  rarely,  for  counter-dies.  When  type- 
metal  is  used  as  a  counter  to  a  zinc  die,  it  is  improved  for  the 
purpose  by  adding  to  it  an  equal  quantity  of  lead  ;  it  may  also 
be  used  in  the  form  of  a  die  in  connection  with  a  lead  counter 
after  rough  stamping  with  zinc. 

Fusible  Alloys. — The  alloy  known  as  Rose's  fusible  metal  is 
composed  of  two  parts  of  bismuth  to  one  of  lead  and  one  of  tin, 
and  melts  at  about  200°  F.  A  still  more  fusible  alloy  is  com- 
posed of  lead  3  parts,  tin  2  parts,  and  bismuth  5  parts,  which  fuses 
at  197°.  There  are  other  alloys  of  lead,  to  be  mentioned  here- 
after, melting  at  from  200°  to  440°,  which  may  be  advantage- 
ously employed  in  forming  dies  to  be  used  after  zinc,  where  the 
latter,  from  its  greater  shrinkage,  fails  to  bring  the  plate  into 
accurate  adaptation  to  the  mouth. 

Soft  Solder  is  an  alloy  composed  of  lead  and  tin  in  the  pro- 
portion of  two  parts  of  the  former  to  one  of  the  latter. 


TIN ANTIMONY.  12^ 


TIN. 

Sn  (Stannum). 


Properties. — Tin  is  a  brilliant,  silver-white  metal,  the  luster 
of  which  is  not  sensibly  affected  by  exposure  to  the  air,  but  is 
easily  oxidized  by  heat.  It  has  a  slightly  disagreeable  taste,  and 
emits,  when  rubbed,  a  peculiar  odor.  It  is  soft,  inelastic,  and, 
when  bent,  emits  a  peculiar  cracking  sound  called  the  creaking 
of  tin.  It  is  inferior  in  tenacity  and  ductility,  but  is  very 
malleable,  and  may  be  beaten  into  leaves  20V0  o^  ^^  inch  in 
thickness,  ordinary//;/  foil  being  about  ^^^-^  of  an  inch  thick. 

The  Fusing  Point  of  tin  is  about  450°  F. ;  it  boils  at  a  white 
heat,  and  burns  with  a  blue  flame  to  binoxid. 

The  more  Common  Alloys  of  tin  with  other  metals  have 
already  been  noticed.  It  was  at  one  time  used  as  a  base  for 
artificial  teeth,  and  more  recently  it  has  been  introduced  as  a 
component  of  "  cheoplastic  "  metal,  a  compound  used  for  the 
same  purpose.  In  its  pure  state,  it  is  sometimes  used  for 
counter-dies,  and  occasionally  for  dies.  When  employed  for  the 
latter  purpose  in  connection  with  a  lead  counter,  the  latter 
should  not  be  obtained  directly  from  the  die,  as  the  high  tem- 
perature of  melted  lead  would  produce,  when  poured  upon  the 
tin,  partial  fusion  of  the  latter  and  consequent  adhesion  of  the 
two  pieces.  Tin  is  also  used  by  many  operators  as  a  trial  base- 
plate for  artificial  dentures,  instead  of  wax,  gutta-percha,  or 
other  more  pliable  materials. 

ANTIMONY. 
Sb  (Stibium). 

General  Properties. — Antimony  is  of  a  silver-white  color, 
with  a  tinge  of  blue,  a  lamellar  texture,  and  a  crystalline  fracture. 
It  is  brittle  and  easily  pulverized.  It  enters  as  an  ingredient  into 
the  composition  of  type  and  stereotype  metal,  music  plates,  and 
Britannia  metal.  It  is  also  a  component  of  certain  fusible  alloys 
analogous  to  those  already  mentioned  under  the  head  of  lead, 
and  which,  in  the  form  of  a  die,  are  sometimes  used  on  account 
of  their  slight  degree  of  shrinkage. 


126  MECHANICAL    DENTISTRY. 

The  Fusing  Point  of  antimony  is  840°  F.,  and  when  heated  at 
the  blowpipe  it  melts  with  great  readiness,  and  diffuses  white 
vapors,  emitting  an  odor  similar  to  garlic.  The  specific  gravity 
of  the  purest  variety  is  6.715. 


BISMUTH. 
Ei  (Bismuthum). 

General  Properties. — Bismuth  is  a  white-colored  metal,  re- 
sembling, in  some  degree,  antimony.  It  is  soft,  but  so  brittle  as 
to  be  easily  pulverized.  Its  specific  gravity  is  9.83,  which  may 
be  increased  somewhat  by  hammering. 

The  Fusing  Point  of  bismuth  is  about  510°  F.  When  the 
temperature  of  the  metal  is  raised  from  32°  to  212°  it  expands 
ih  "">  length. 

Alloyed  with  Other  Metals. — Bismuth  has  the  property,  in 
a  high  degree,  of  increasing  the  fusibility  of  the  metals  with  which 
it  is  incorporated,  and  is  a  common  ingredient  of  the  more  fusible 
alloys,  some  of  which  melt  in  boiling  water.  One  part  of  bismuth 
with  24  of  tin  is  malleable,  but  the  alloy  of  these  metals  becomes 
brittle  by  the  addition  of  more  bismuth.  Bismuth  unites  readily 
with  antimony,  and  in  the  proportion  of  one  part  or  more  of  the 
former  to  two  of  the  latter,  it  expands  in  the  act  of  cooling. 

There  are  many  other  metals  and  alloys  besides  those  already 
enumerated,  but  which  have  not  been  particularly  described  on 
account  of  their  inutility  in  the  laboratory  for  dental  purposes. 
Among  these  maybe  mentioned  iro)i, brass,  bronze,  etc.,  which  are 
only  employed  for  au.xiliary  purposes,  and  are  both  inconvenient 
and  impracticable  for  dies  by  reason  of  their  infusible  nature  and 
consequent  contraction;  nickel,  on  account,  also,  of  its  extreme 
infusibility  and  its  tendency  to  render  the  alloy  of  which  it  is  a 
component  less  fusible  ;  sodium,  on  account  of  the  changes  pro- 
duced on  it  by  exposure  to  the  air;  potassinvi,  on  account  of  its 
extreme  sensitiveness  to  the  influence  of  low  temperatures,  being 
semi-fluid  at  60°  Fahr.,  nearly  liquid  at  92°,  and  entirely  so  at 
120°  ;  «;'iT;«<:, because  it  volatilizes  before  fusing;  cadnm(m,^\t\\ 
no  advantages  above  tin,  on  account  of  its  scarcity,  costliness, 
etc. 


CHAPTER  XI. 

GENERAL  PROPERTIES  OF  ALLOYS,  AND  THEIR  TREATMENT 
AND  BEHAVIOR  IN  THE  PROCESS  OF  COMPOUNDING. 

All  alloys  possess  metallic  luster,  are  opaque,  conduct  heat  and 
electricity,  and,  in  a  greater  or  less  degree,  are  ductile,  malleable, 
elastic  and  sonorous.  Some  alloys,  as  brass  and  gong  metal, 
are  usually  malleable  in  the  cold  and  brittle  when  hot. 

Metals  sometimes  unite  in  atomic  ratios,  forming  compounds 
of  definite  or  equivalent  proportions  of  the  component  metals,  as 
certain  alloys  of  copper  and  zinc,  gold  and  copper,  gold  and 
silver,  mercurial  alloys,  etc.,  while,  on  the  other  hand,  many  are 
formed  in  all  proportions,  like  mixtures  of  salt  and  water. 

Metals  differ  in  respect  to  their  affinity  for  each  other,  and  do 
not,  therefore,  alloy  with  equal  facility  ;  thus  it  is  difficult  to 
unite  silver  and  iron,  but  the  former  combines  readily  with  gold, 
copper,  or  lead. 

The  Ductility  of  an  Alloy  is,  in  general,  less  than  that  of 
its  constituent  metals,  and  this  difference  is,  in  some  instances, 
remarkably  prominent,  as  in  the  case  of  certain  alloys  of  copper 
and  tin,  already  mentioned. 

An  alloy  is  generally  harder  than  the  mean  hardness  of  its 
components,  a  property  which,  when  taken  in  connection  with 
their  increased  fusibility,  gives  to  alloys  peculiar  value  in  the 
formation  of  dies  for  stamping  purposes.  To  the  rule  stated, 
amalgams,  or  mercurial  alloys,  are  cited  as  exceptions. 

The  Density  of  an  Alloy  varies  with  the  peculiar  metals 
composing  it,  being  generally  either  greater  or  less  than  the  mean 
density  of  its  several  components. 

It  is  impossible  to  predict  with  certainty  the  melting  point  of 
an  alloy  from  that  of  its  separate  constituents,  but,  generally,  the 
fusibility  of  the  alloy  is  increased,  sometimes  in  a  most  remark- 
able degree.  The  alloy  of  5  parts  of  bismuth,  3  of  lead, 
and  2  of  tin  is  a  striking  example  of  this  fact,  this  compound 

127 


128  MECHANICAL    DENTISTRY. 

melting  at  197°,  while  the  mean  melting  point  of  its  constituents 
is  514°.  Silver  solder  is  also  a  familiar  illustration  of  the  influence 
of  alloying  on  the  fusibility  of  metals;  copper,  melting  at  1996°, 
and  silver  at  1873°,  when  combined  fuse  at  a  heat  much  below 
that  required  to  melt  silver,  the  more  fusible  component  of  the 
alloy.  Again,  iron,  which  melts  at  a  little  less  than  3000°,  ac- 
quires almost  the  fusibility  of  gold  when  alloyed  with  the  latter. 
Examples  might  be  multiplied,  but  it  will  be  sufficient  to  add 
that,  in  general,  metallic  alloys  vicltat  a  knver  heat  than  is  required 
to  fuse  the  most  refractory  or  infusible  component,  and  sometimes  than 
the  most  fusible  ingredient. 

The  Color  of  an  Alloy  cannot,  in  general,  be  inferred  from 
that  of  its  component  metals  ;  thus  it  would  be  conjectured  that 
copper  would  be  rendered  very  much  paler  by  adding  to  it  zinc 
in  considerable  quantities,  but  the  fallacy  of  such  an  inference 
is  at  once  shown  by  an  examination  of  some  of  the  rich-looking 
gold-colored  varieties  of  brass,  as  Prince's  metal,  pinchbeck,  and 
similor,  composed  each  of  nearly  equal  parts  of  copper  and  zinc  ; 
and  Manheim  gold,  compounded  of  3  parts  copper  and  i  of  zinc. 

The  Affinity  of  an  Alloy  for  Oxygen  is  greater  than  that  of 
the  separate  metals,  a  phenomenon  that  is  ascribed  by  Ure  to  the 
increase  of  affinity  for  oxygen  which  results  from  the  tendency 
of  one  of  the  oxids  to  combine  with  the  other ;  by  others  it  is 
attributed  to  galvanic  action.  According  to  Faraday,  lOO  parts 
of  steel  alloyed  with  one  of  platinum  is  dissolved  with  efferves- 
cence in  dilute  sulphuric  acid  too  weak  to  act  with  perceptible 
energy  on  common  steel.  It  is  offered  in  explanation  of  this 
fact  that  the  steel  is  rendered  positive  by  the  presence  of  plati- 
num. A  similar  illustration  is  afforded  by  the  action  of  dilute 
acid  on  commercial  zinc,  which  is  usually  an  alloy  of  zinc  with 
other  metals. 

The  action  of  air  is,  in  general,  less  on  alloys  than  on  the 
separate  metals  composing  them.  To  this,  however,  there  are 
exceptions,  as  the  alloy  of  3  parts  of  lead  and  i  of  tin,  which, 
when  heated  to  redness,  burns  briskly  into  a  red  oxid. 

Some  points  of  practical  interest  suggest  themselves  in  con- 
nection with  the  behavior  and  proper  management  of  alloys  in 
the  process  of  compounding. 


PROPERTIES  AND  TREATMENT  OF  ALLOYS.         1 29 

As  metallic  alloys  can  only  be  formed  by  fusion,  and  as  the 
affinity  of  the  metals  composing  them  for  oxygen  is  greatly  in- 
creased by  heat,  especially  those  denominated  base,  it  is  import- 
ant that  this  tendency,  which  is  incompatible  with  the  proportional 
accurateness  of  the  compound,  should  be,  as  far  as  practicable, 
guarded  against.  Hence,  various  substances  having  a  greater 
affinity  for  oxygen  than  the  metals  to  be  united,  as  oil  or  grease, 
rosin,  powdered  charcoal,  etc.,  are  generally  added,  coating  the 
surface  of  the  liquid  metals,  and  which,  by  affording  a  protective 
covering,  preserve,  with  little  change,  the  proportions  of  the 
alloy. 

The  Difficulty  of  Securing  a  Homogeneous  Alloy,  Owing 
to  the  Difference  in  the-  Specific  Gravities  of  the  Metals 
Composing  It. — Some  difficulty  is  occasionally  experienced  in 
obtaining  a  perfectly  uniform  alloy,  on  account  of  the  different 
specific  gravities  of  the  metals  composing  it — each  metal  assum- 
ing the  level  due  to  its  density.  This  partial  separation  is  com- 
mon to  gold  and  silver,  provided  they  have  not  been  adequately 
stirred  before  pouring.  This  result  is  not  so  likely  to  occur  when 
the  metals  employed  are  in  small  quantities  and  are  suddenly 
cooled,  but  when  used  in  considerable  masses  and  allowed  to 
cool  slowly,  it  is  much  favored  by  permitting  the  metals  to  fix 
themselves  in  the  order  of  their  separate  densities.  Hence, 
whenever  a  notable  difference  in  the  specific  gravity  of  the  metals 
exists,  the  fused  mass  should  be  briskly  stirred  immediately 
before  the  instant  of  pouring  it,  and  should  be  made  to  solidify 
quickly.  If  uniformity  be  not  obtained  in  this  manner,  it  will  be 
necessary  to  remelt,  and  repeat  the  process  until  the  alloy  is 
rendered  sufficiently  homogeneous. 

The  Metals  that  Should  be  Melted  First. — In  alloying 
three  or  more  metals  differing  greatly  in  fusibility,  or  that  have 
but  little  affinity  for  each  other,  it  is  better  to  first  unite  those 
which  most  readily  combine,  and  afterward,  these  with  the  re- 
maining metal  or  metals.  If,  for  example,  it  is  desired  to  unite 
a  small  quantity  of  lead  with  brass  or  bronze,  some  difficulty 
would  be  experienced  in  forming  the  alloy  by  direct  incorporation 
of  the  metals,  but  union  could  be  readily  effected  by  first  melt- 
ing the  lead  with  zinc  or  tin,  and  then  adding  the  melted  copper, 
9 


PART  SECOND. 


ARTIFICIAL  DENTURES. 

Before  considering  particularly  the  distinct  and  special  methods 
employed  in  the  construction  of  artificial  dentures,  such  prelimin- 
ary processes  as  are  common  in  some  degree  to  all,  will,  for  the 
sake  of  convenient  arrangement,  and  the  avoidance  of  unnecessary 
repetition  hereafter,  be  first  considered.  These  processes  relate  : 
I.  To  the  treatment  of  the  mouth  preparatory  to  the  insertion  of 
artificial  teeth.  2.  The  manner  of  obtaining  impressions  of  the 
mouth.  3.  The  manner  of  procuring  and  forming  plaster  models 
of  the  mouth.     4.   Metallic  dies  and  counter-dies. 


CHAPTER  I. 

TREATMENT  OF  THE  MOUTH  PREPARATORY  TO  THE  INSER- 
TION OF  ARTIFICIAL  DENTURES. 

It  rarely  occurs  that  all  the  structures  of  the  mouth  are  in  such 
condition  as  will  render  it  proper  to  insert  an  artificial  appliance 
without  some  preparatory  treatment.  This  important  require- 
ment cannot,  in  any  material  respect,  be  disregarded  by  the  prac- 
titioner without  endangering  the  utility  and  permanence  of  the 
substitute,  and  inflicting  upon  the  patient  a  train  of  consequences 
alike  distressing  and  pernicious.  Every  experienced  dentist  is 
familiar  with  the  fact  that  an  artificial  substitute,  resting  upon 
diseased  roots  of  teeth  and  impinging  continually  upon  gums 
already  irritated  and  inflamed,  soon  becomes  a  source  not  only  of 
annoyance  and  discomfort  to  the  patient,  but  is  rendered,  in  a 
great  degree,  inefficient  in  the  performance  of  some  of  its  more 
important  offices.  There  is,  besides,  a  perpetual  and  cumulative 
aggravation  of  the  morbid  conditions,  and  sooner  or  later  irre- 
trievable destruction  of  the  remaining  natural  organs  will  be 
induced.  These  consequences  cannot  be  wholly  averted  by  the 
most  skilful  manipulation,  but  they  may  be  greatly  magnified  by 
a  defective  execution  of  the  work,  or  by  a  faulty  adaptation  of 
the  appliance  to  the  parts  in  the  mouth. 

Patients  not  infrequently  attempt,  by  every  artifice  or  pretext 
that  caprice  or  timidity  may  suggest,  to  persuade  the  operator  to 
violate  his  own  clear  convictions  of  duty,  but,  unless  under  cir- 
cumstances of  peculiar  exigency,  he  should  be  careful  to  guard 
himself  against  the  imputation  of  incompetency  or  bad  faith  by 
being  peremptory  and  unyielding  in  his  demands  upon  the  patient 
to  submit  to  the  necessities  and  just  requirements  of  the  case,  and 
no  ordinary  circumstance  should  influence  him  in  opposition  to 
his  better  informed  judgment. 

The  conditions  usually  met  with,  to  which  it  will  be  necessary 
to  direct  attention  in  the  treatment  of  the  mouth,  are  :    i.  The 

132 


PREPARATORY    TREATMENT    OF    THE    MOUTH.  1 33 

presence  of  useless  and  diseased  remains  of  teeth.  2.  Accumula- 
tions of  tartar.  3.  Diseased  states  of  the  gums  and  mucous 
membrane.     4.  Caries. 

Useless  and  Diseased  Remains  of  Teeth. — It  may  be  stated, 
as  an  absolute  rule  of  practice,  that  all  teeth,  or  remains  of  teeth, 
affected  by  incurable  forms  of  disease,  should  be  removed  before 
inserting  either  partial  or  entire  dentures.  This  recommendation 
must,  however,  be  construed  in  the  light  of  the  curative  resources 
of  dental  surgery  and  therapeutics.  Many  diseased  conditions 
associated  with  the  teeth  that  have  heretofore  been  generally  re- 
garded as  incurable,  have,  in  the  use  of  more  radical  and  efficient 
remedial  measures,  proven  amenable  to  such  treatment  as  as- 
sures their  retention  for  many  years  in  a  condition  fitting  them 
for  important  uses'.  A  new  impulse  has  of  late  been  given  to 
such  conservative  treatment  of  these  organs  with  the  view, 
chiefly,  of  utilizing  them  more  generally  for  purposes  of  support 
in  setting  artificial  crowns,  and  in  the  method  of  replacement 
known  as  "  bridge-work." 

The  marked  success  which  of  late  years  has  attended  the 
treatment  of  diseased  roots,  and  the  increasing  importance  at- 
tached to  them  for  the  purposes  mentioned,  as  well  also  as  the 
essential  office  they  perform  in  preserving  the  structural  integrity 
of  the  associated  alveoli,  and  in  maintaining  the  normal  circula- 
tion and  nutrition  of  the  parts,  would  seem  to  justify  the  con- 
clusion that  their  extraction  is  plainly  contra-indicated,  save  in 
rare  and  exceptional  cases  of  intractable  disease,  in  which  case  there 
is  no  question  concerning  the  propriety  or  necessity  of  their 
removal.  Their  presence  in  connection  with  the  substitute  must, 
sooner  or  later,  become  not  only  a  source  of  annoyance  and  dis- 
tress to  the  patient,  but  will,  in  all  probability,  lead  ultimately 
to  consequences  of  a  still  graver  nature.  Inflammation  and 
suppuration  will  be  likely  to  be  induced,  or,  if  already  present, 
will  be  aggravated  by  the  mobility  and  unaccustomed  pressure 
of  the  substitute  in  the  process  of  mastication,  thus  contamina- 
ting and  vitiating  the  oral  secretions,  which  act,  by  reason  there- 
of, with  increasing  energy  upon  oxidizable  materials  present  in 
the  mouth,  as  well  as  upon  the  remaining  natural  teeth,  while 
the  contiguous  parts,  through  their    immediate    connection  or 


134  MECHANICAL    DENTISTRY. 

sympathetic  relations  with  the  structures  of  the  mouth,  respond  to 
the  local  disturbances,  and  the  case,  in  time,  becomes  complicated 
with  those  various  distressing  maladies  about  the  head  and  face  so 
commonly  associated  with  diseased  conditions  of  the  oral  cavity. 
At  last,  the  patient,  no  longer  able  to  endure  the  offensiveness 
and  distress  arising  from  the  presence  of  the  substitute  in  the 
mouth,  or  to  properly  masticate  his  food,  is  compelled  to  have 
the  offending  organs  removed.  The  absorption  of  the  gums 
and  processes  which  follows  this  operation,  and  the  corres- 
ponding changes  which  occur  therefrom  in  the  form  of  the  al- 
veolar ridge,  make  it  imperative  either  to  reconstruct  the  piece  or 
to  supply  the  patient  with  an  entirely  new  substitute  ;  whereas, 
if  due  regard  had  been  given  to  the  proper  preparation  of  the 
mouth  in  the  first  instance,  the  patient  might  be  spared  such  in- 
flictions, and  the  operator  the  discredit  which  almost  invariably 
attaches  to  the  neglect  of  the  measures  recommended. 

Removal  of  Salivary  Calculus  or  Tartar. — The  deposits  of 
tartar  which  so  frequently  collect  at  the  necks  of  the  teeth  and 
under  the  free  margins  of  the  gum  are  a  prolific  source  of  evil, 
inducing  ultimate  destruction  of  the  investing  membranes  and 
contiguous  alveoli,  and  as  this  deposit  is  continuous  and  pro- 
gressive; following  closely  the  wasting  or  destruction  of  the  im- 
plicated tissue,  teeth  originally  firm  become  in  time  not  only 
unfitted  for  the  proper  performance  of  the  functions  required  of 
them,  but  a  source  of  diseased  action  in  surrounding  structures. 
Hence  it  becomes  absolutely  necessary,  as  it  relates  to  the  gen- 
eral health  of  the  mouth,  to  thoroughly  remove,  with  suitable 
instruments,  all  traces  of  this  concretion  from  the  teeth.  In  some 
complications  characterized  by  suppurating  processes  and 
necrosed  alveoli,  as  in  so-called  "  Rigg's  disease,"  or  pyorrhea 
alveolaris,  the  treatment  must  be  more  thorough  and  radical. 

Diseased  Conditions  of  the  Mucous  Membrane  and  Gums. 
— It  will  seldom  be  necessary  to  institute  treatment  for  the  re- 
duction of  inflammation  and  suppuration  of  the  soft  tissues  of 
the  mouth  after  removal  of  diseased  roots  and  tartar,  inasmuch 
as  these  conditions,  being  generally  provoked  by  and  associated 
with  the  latter,  will  spontaneously  subside  with  the  removal 
of  the  exciting  causes.     If,  however,  this  does  not  occur  within 


PREPARATORY   TREATMENT    OF   THE    MOUTH.  1 35 

a  reasonable  time,  relief  may  generally  be  obtained  with  the  use, 
as  a  mouth-wash,  of  any  of  the  remedies  ordinarily  employed,  as 
dilute  tincture  of  arnica,  myrrh  or  calendula,  phenol  sodique,  etc. 
As  a  means  of  allaying  soreness  or  tenderness  of  the  gums  after 
extraction,  the  writer  has  had  gratifying  success  in  the  use  of 
Pond's  extract  of  hamamelis.  If  there  are  morbid  conditions  of 
the  soft  tissues  or  osseous  structures  of  the  mouth,  not  imme- 
diately arising  from  the  presence  of  diseased  roots  and  tartar, 
they  should  be  treated  in  accordance  with  the  particular  patho- 
logical conditions  present. 

Caries  or  Decay  of  the  Remaining  Teeth. — In  order  that 
all  the  teeth  which  it  is  deemed  advisable  to  retain  in  the  mouth 
may  be  permanently  preserved,  it  will  be  necessary  to  fill,  or 
otherwise  treat,  such  as  maybe  affected  by  caries.  This  opera- 
tion will  be  attended  with  more  satisfactory  results,  and  be 
accompanied  with  less  pain  to  the  patient  and  diminished  risk 
of  failure,  when  performed  after  the  removal  of  the  roots  of  teeth 
and  tartar,  and  the  restoration  of  diseased  conditions  of  the 
mouth  to  health,  as,  in  this  case,  there  will  be  less  irritability  of 
the  general  system  and  reduced  sensitiveness  of  the  teeth  oper- 
ated on. 

Surgical  Treatment  of  the  Mouth  after  the  Extraction  of 
Teeth. — In  the  operation  of  extracting  preparatory  to  the  in- 
sertion of  artificial  dentures,  especially  in  cases  accompanied  by 
unavoidable  fracture  of  the  processes,  it  sometimes  happens  that 
loose  and  pendulous  portions  of  gum  remain,  giving  temporary 
annoyance  to  the  patient.  Any  considerable  excess  of  such 
tissue  may  be,  in  part  at  least,  clipped  off,  while  sharp  and  pro- 
truding portions  of  processes  at  other  points  should  be  removed, 
for,  if  allowed  to  remain,  the  gum  closing  over  them  will,  in 
a  short  time,  become  irritated  and  inflamed,  and  exceedingly 
painful  to  the  slightest  pressure.  If,  in  the  course  of  a  few 
weeks,  prominences  still  remain,  over  which  the  mucous  mem- 
brane is  stretched  and  irritated  or  inflamed,  as  is  more  frequently 
the  case  around  the  sockets  of  the  cuspidati,  the  membrane 
should  be  divided  over  such  points  with  a  lancet,  and  the  sharp 
points  of  bone  underneath  broken  down  with  suitable  cutting 
instruments.     This  condition,  however,  can  usually  be  obviated. 


136  MECHANICAL    DENTISTRY. 

in  a  measure,  by  firmly  pressing  the  process  together  immedi- 
ately after  extraction. 

Time  Necessary  to  Elapse  after  the  Extraction  of  Teeth 
before  Inserting  Artificial  Dentures. — The  time  that  should 
elapse  after  extracting  the  natural  teeth,  before  replacing  them 
with  artificial  substitutes,  will  depend  upon  various  circumstances. 
If  the  appliance  is  only  intended  to  meet  the  wants  of  the  in- 
dividual until  all  the  changes  effected  by  absorption  of  the 
gums  and  processes  are  fully  completed,  it  may  be  inserted  in 
from  one  to  three  weeks,  depending  somewhat  upon  the  number 
of  teeth  extracted,the  extent  of  the  injuries  unavoidably  inflicted 
upon  the  parts,  and  the  virulence  of  the  diseased  action  present 
in  the  structures  of  the  mouth  at  the  time  of  the  operation.  If 
there  are  no  unusual  complications,  and  the  space  or  spaces  to 
be  supplied  are  such  as  are  made  by  the  loss  of  only  one  or  two 
teeth  at  intervals,  the  parts  quickly  assume  their  normal  con- 
dition, and  the  piece  to  be  temporarily  worn  may  be  applied 
within  a  few  days.  If,  however,  a  greater  number  or  all  of  the 
teeth  have  been  removed,  more  or  less  inflammation  and  tender- 
ness will  be  present  for  from  ten  days  to  two  or  three  weeks, 
rendering  the  wearing  of  an  artificial  piece  uncomfortable  to  the 
patient,  and  in  some  degree  mischievous,  by  aggravating  the 
morbid  conditions  already  existing.  Another  objection  to  the 
too  early  introduction  of  artificial  substitutes  into  the  mouth 
arises  from  the  fact  that  the  changes  which  occur  in  the  ridge 
are  much  more  rapid  within  the  first  few  weeks  after  the  extrac- 
tion of  the  teeth  than  at  any  subsequent  period,  so  that  the  plate, 
if  inserted  immediately  or  within  a  few  days  after  such  an  opera- 
tion, will  soon  lose  its  bearing  upon  the  ridge  and  become  ineffi- 
cient for  masticating  purposes,  or  may  even  fail  to  be  retained  in 
the  mouth  without  much  annoyance  to  the  patient.  From  two 
to  eight  or  more  weeks,  should  therefore,  elapse  before  inserting 
the  substitute.  In  the  meantime,  the  patient  should  be  seen 
frequently,  and  such  medical  or  surgical  treatment  adopted  from 
time  to  time  as  the  case  may  demand. 

The  time  occupied  in  the  completion  of  those  changes  which 
occur  in  the  alveolar  border  after  the  extraction  of  all  or  any 
considerable  number  of  the  teeth  cannot  be  definitely  stated,  but 


PREPARATORY  TREATMENT  OF  THE  MOUTH.        I  37 

will  range  from  five  to  eighteen  months  or  more,  according  to 
the  amount  of  superfluous  structures  to  be  removed,  the  density 
of  the  osseous  tissues,  and  the  functional  activity  of  the  absorb- 
ents. In  all  cases,  ample  time  should  be  permitted  to  elapse  in 
order  that  no  appreciable  change  in  the  form  of  the  parts  may 
take  place  after  the  appliance  has  been  permanently  adjusted. 
It  should  be  remembered,  however,  that  there  is  no  period  of 
time  when  the  changes  in  the  maxillary  bones  which  follow  the 
extraction  of  the  natural  teeth  may  be  said  to  be  absolutely 
completed.  It  is  well  known  that,  in  exceptional  cases,  renewed 
absorption  may  occur  long  after  the  time  when  it  is  supposed  to 
be  completed,  extending  in  some  cases  quite  beyond  the 
ordinary  limits.  This  is  ascribed  by  many  to  misfitting  plates, 
or  to  some  particular  quality  of  the  material  used  as  a  base, 
notably  vulcanized  rubber.  While  there  may  be  some  plausi- 
bility in  this  view,  it  can  hardly  be  accepted  as  final  or  conclu- 
sive. That  the  unusual  destruction  or  wasting  away  of  involved 
tissue  is  induced  by  some  abnormal  action  of  the  absorbent  or 
nutritive  processes  is  without  question,  but  whether  this  is 
induced  by  local  or  systemic  causes  remains  in  doubt. 


CHAPTER  II. 

MATERIALS,  APPLIANCES,  AND  METHODS  EMPLOYED  IN 
OBTAINING  IMPRESSIONS  OF  THE  MOUTH. 

Ill  the  process  of  constructing  a  dental  substitute,  it  is  of  the 
first  importance  that  as  accurate  an  impression  as  possible  should 
be  obtained  of  all  those  parts  of  the  mouth  with  which  the  appli- 
ance is  any  way  connected.  If  tins  important  preliminary  step  is 
in  any  essential  respect  imperfectly  performed,  the  ultimate  utility  of 
the  artificial  fixture  will  either  be  greatly  impaired  or  ivliolly  de- 
stroyed, notwithstanding  all  the  subsequent  manipulations  may 
be  most  carefully  and  skilfully  performed.  The  operator,  there- 
fore, should  not  only  avail  himself  of  every  appliance  and  facility 
that  will  enable  him  to  attain  the  most  perfect  results,  but  should 
have  an  exact  and  intelligent  acquaintance  with  the  nature,  pro- 
perties, and  adaptability  of  the  impression  materials  used. 

The  substances  usually  employed  for  this  purpose  are  :  bees- 
wax, modeling  composition,  and  plaster-of- Paris. 

Some  diversity  of  opinion  exists  as  to  the  relative  value  of 
these  several  impression  materials,  and  the  choice  of  any  one  of 
the  class  is  generally  determined  by  individual  notions  of  the  in- 
dications to  be  fulfilled  in  any  given  case,  and  the  supposed 
special  adaptability  of  the  material  to  the  fulfilment  of  such  indi- 
cations. 

In  the  case  of  entire  dentures,  where  there  is  a  near  approach  to 
uniformity  of  hardness  or  softness,  and  consequent  uniformity  of 
resistance,  in  the  tissues  of  the  mouth,  plaster,  of  the  proper  con- 
sistency, unquestionably  takes  precedence  of  all  other  materials 
for  the  purpose,  and  the  almost  universal  preference  given  to  it 
in  such  cases  is  a  virtual  confession  of  its  superior  fitness.  Its 
capability,  beyond  that  of  all  the  other  substances  mentioned,  of 
securing  the  most  perfect  impression  of  the  several  parts  in  their 
undisturbed  relation  to  each  other  is  unquestioned,  and  it  may 
be  affirmed  with  positiveness   that,  except,  possibly,  in  the  case 

138 


IMPRESSIONS    OF    THE    MOUTH.  1 39 

of  plastic  bases,  where  there  is  no  compensation  for  the  slight 
expansion  of  the  plaster,  if  all  the  surfaces  on  which  the  substi- 
tute rests  were  equally  pliant  or  equally  resistant  to  forces  applied 
to  them,  no  other  material  would  be  required.  But,  strictly 
speaking,  this  condition  of  uniformity  never  prevails,  and  in  many 
cases  there  is  a  marked  departure  from  it.  The  most  common 
and  troublesome  complication  of  this  kind  occurs  where  there  is 
a  more  or  less  pliable  or  yielding  condition  of  the  alveolar  ridge 
associated  with  a  comparatively  hard  and  resistant  surface  along 
the  median  line  of  the  floor  of  the  palate,  being  more  pronounced 
near  the  soft  palate.  In  such  cases,  this  inequality  of  softness 
and  hardness,  if  considerable,  prevents  a  properly  balanced  con- 
tact and  pressure  of  a  substitute  constructed  from  an  impression 
of  the  parts  in  a  state  of  repose.  Thus,  for  example,  in  the  case 
of  a  perfectly  fitting  denture  secured  in  the  manner  just  stated, 
if  the  ridge  along  the  mesial  line  of  the  palatal  vault  is  more  than 
usually  hard  and  prominent,  and  the  lateral  portion  of  the  arch 
and  alveolar  ridge  relatively  soft  and  yielding,  the  substitute, 
meeting  with  a  fixed  point  of  resistance  at  the  floor  of  the  palate, 
will  prevent  the  lateral  walls  and  ridge  from  being  sufficiently 
compressed  on  the  application  of  retaining  forces,  whether  atmos- 
pheric, adhesive,  or  capillary,  or  all  combined.  Hence,  when 
forcible  pressure  is  made  on  one  side  over  the  ridge,  as  in  masti- 
cation, the  substitute,  impinging  or  riding  upon  the  central 
resistant  surface  of  the  arch,  as  upon  a  pivotal  point,  will  be 
detached  and  thrown  off  from  the  opposite  side.  If  the  same 
yielding  condition  of  the  anterior  portion  of  the  ridge  prevails, 
the  application,  when  forces  are  applied  to  the  front  teeth,  will  be 
dislodged  posteriorly. 

The  proposed  remedy  for  the  instability  of  the  substitute,  re- 
sulting from  the  conditions  mentioned,  consists  in  so  constructing 
the  dental  appliance  that,  v/hen  applied  to  the  mouth  and  sub- 
jected to  the  action  of  the  retaining  forces,  a  degree  of  resistance 
in  those  parts  where  the  soft  tissues  are  in  excess  will,  through 
compression  of  the  tissues,  be  secured,  equal,  or  nearly  so,  to 
that  presented  by  the  central  portion  of  the  arch  ;  in  other  w^ords, 
by  establishing  an  equilibrium  of  pressure  or  resistance  in  all  the 
parts  on  which  the  plate  rests. 


140  MECHANICAL    DENTISTRY. 

It  is  generally  believed  that  certain  forms  of  impression  ma- 
terial, through  the  pressure  they  exert,  are  capable  of  contribut- 
ing materially  to  this  result.  This  is  predicated  on  the  assumption 
that  the  pressure  they  exert  is  sufficient  to  compress  or  displace 
the  tissues  in  question.  It  may  be  well  to  inquire  if  the  com- 
pressing power  of  these  substances,  in  the  cases  under  consider- 
ation, has  not  been  overrated.  If  by  the  term  compression,  as 
used  in  this  connection,  is  meant  condensation  or  diminished 
bulk  of  tissue,  certainly  no  such  result  could  be  obtained  by  any 
force  capable  of  being  applied  within  the  mouth,  however  hard 
and  resistant  the  material  used.  Any  change  in  the  normal 
configuration  of  the  arch  and  ridges  possible  in  the  use  of  such 
substances  must,  therefore,  result,  not  in  condensation,  but  in 
displacenicnt  of  tiss7ic.  It  can  be  readily  understood  how  this 
displacement  may  occur  along  the  summit  line  of  the  ridge  in 
cases  characterized  by  considerable  excess  of  gum  material  lying 
in  loose  and  gristly  folds,  chiefly  in  front  of  the  bicuspids,  and 
associated  generally  with  the  long  use  of  partial  dentures.  In 
applying  pressure  in  such  cases,  the  effect  would  be  to  force 
these  mobile  structures  out  of  their  customary  relations  to  the 
ridge  and  arch.  How  far  such  a  procedure  is  in  accordance 
with  the  principles  of  correct  practice  must  be  submitted  to 
individual  judgment.  That  any  change  in  the  mere  relative 
position  of  such  loose  structures  to  the  ridge  would  contribute 
in  any  appreciable  manner  to  the  stability  of  the  substitute  is 
not  very  apparent. 

Within  the  limits  of  the  maxillary  arch  or  palatal  vault,  the 
fossae  or  depressions  lying  on  either  side  of  the  central  line  are 
filled  more  or  less  completely  with  a  mass  of  comparatively  soft 
but  elastic  areolar,  cellular,  or  connective  tissue,  which,  in  its 
unchanged  condition,  is  thought  to  practically  interfere,  in  many 
cases,  with  a  properly  balanced  contact  or  bearing  of  the  substi- 
tute. A  partial  remedy,  at  least,  it  is  claimed  by  many,  may  be 
found  in  the  use  of  some  impression  material  of  sufficient  firmness 
to  compress  or  displace  such  tissues  sufficiently  to  afford  points 
of  resistance  to  the  substitute  equal,  or  nearly  so,  to  that  offered 
by  the  median  line  of  the  arch.  The  displacement  here,  if  any, 
would  be  in  the  direction  of  the  least  resistance,  or  toward  the 


IMPRESSIONS    OF    THE    MOUTH.  I4I 

velum  or  soft  palate,  all  portions  of  the  arch  anterior  to  the 
latter,  except  in  the  case  of  an  air  chamber,  offering  effectual 
resistance  to  displacement  in  any  other  direction.  When  the 
nature  and  relations  of  these  associated  soft  structures  of  the 
mouth  are  considered,  it  is  highly  improbable,  and  we  think 
impossible,  that  any  appreciable  change  of  contour  within  the 
arch  could  take  place  on  the  application  of  any  force  applied  in 
the  use  of  either  wax  or  modeling  composition.  If  these  con- 
clusions should  be  justified  by  experimental  tests,  as  we  believe 
they  would  be,  it  would  be  practically  unimportant,  except  w;here 
the  tissues  of  the  ridge  are  characterized  by  unusual  mobility, 
what  material  was  used,  provided  a  perfect  impression  could  be 
obtained  with  it.  The  paramount  merits  of  plaster,  as  a  substance 
capable  beyond  question  of  fulfilling  perfectly  this  requirement, 
would  therefore  recommend  it,  in  preference  to  any  other  mate- 
rial ;  and  we  might  add,  too,  that  the  more  difficulties  there  are 
presented  in  securing  an  accurate  impression,  the  more  reason 
there  is  for  using  plaster-of-Paris  as  the  impression  material. 

One  possible  result  of  the  use  of  any  of  the  impression 
materials  named,  exclusive  of  plaster,  both  in  full  and  partial 
cases,  must  always  render  their  employment  of  doubtful  ex- 
pediency whenever  plaster  can  be  successfully  manipulated  for 
the  same  purpose,  namely,  their  great  liability  to  distortion  on 
the  application  of  forces  necessary  to  detach  them  from  the 
mouth,  and  the  impossibility  of  detecting  any  change  of  form 
until  the  error,  too  late  for  correction,  is  revealed  in  a  faulty 
adaptation  of  the  finished  piece  to  the  mouth.  It  must  not, 
however,  be  understood  from  this  that  it  is  impossible  to  secure 
a  practically  accurate  impression  of  the  parts  in  the  use  of  these 
materials.  The  purpose  is,  rather,  to  impress  the  importance 
and  absolute  necessity  of  extraordinary  care  in  their  manipula- 
tion in  order  to  secure  satisfactory  results.  The  relative 
liability  of  the  several  substances  named  to  such  disturbance  of 
form,  and  the  precautions  necessary  to  avoid  such  an  unfortu- 
nate and  generally  fatal  accident,  will  be  more  particularly 
noticed  when  we  come  to  treat  of  them  individually  as  impres- 
sion materials.     This  will  be  done  in  the  order  before  named*. 

Beeswax. — There   are   two   varieties    of  this   substance    in 


142  MECHANICAL    DENTISTRY. 

common  use,  the  yelloiv  and  ivliite  wax.  The  yellow  variety  is 
esteemed  preferable  to  the  white  on  account  of  its  superior 
toughness ;  the  latter  being,  to  some  extent,  disintegrated,  or 
rendered  less  tenacious,  in  the  process  of  bleaching,  but  is 
frequently  used  and  is  preferred  by  many  on  account  of  its  color. 
The  more  desirable  properties  of  the  yellow  wax  are  often 
impaired  by  the  admixture  with  it  of  tallow,  with  which  it  is,  for 
mercenary  purposes,  frequently  contaminated.  The  presence  of 
tallow  may  be  detected  by  its  characteristic  odor,  and  by  the 
whitish  or  pale  yellow  color  it  imparts  to  the  wax,  which  in  its 
pure  state  is  of  a  deep,  bright  straw  color. 

Wax  used  for  impressions  should  always  be  kept  in  convenient 
form  for  immediate  use,  and  may  be  prepared  either  by  warming 
it  until  sufficiently  soft  and  then  rolling  or  pressing  it  into  thin 
sheets ;  or,  having  melted  it  in  a  properly  formed  vessel,  immerse 
in  it  a  strip  of  thin  board,  previously  moistened,  and  withdraw 
quickly  ;  this  is  repeated  as  the  successive  layers  cool,  until  a 
coating  of  sufficient  thickness  is  obtained.  The  latter  is  a 
convenient  method  of  obtaining  sheets  of  wax  of  a  uniform 
thickness,  a  form  frequently  required  for  various  purposes  in  the 
dental  laboratory. 

The  following  directions  in  the  use  of  wax  will  apply  also  to 
its  combinations  with  paraffine  and  gutta  percha,  and  also  to 
modeling  compositions. 

Manner  of  Obtaining  an  Impression  of  the  Mouth  in  Wax 
for  Partial  Upper  Dentures. — Until  within  the  past  few  years, 
wax  has.  been  used  almost  exclusively  for  the  purpose  of  obtain- 
ing an  impression  of  the  mouth  in  those  cases  where  any  number 
of  the  natural  teeth  remain  in  either  or  both  jaws  ;  for  this  pur- 
pose it  is  ordinarily  more  convenient  and  manageable  than 
plaster,  and,  if  carefully  manipulated,  will  secure  in  many  cases 
a  sufficiently  accurate  impression  of  the  parts. 

Before  preparing  the  wax,  a  suitable  impression  cup  or  tray 
should  be  selected,  conforming  as  nearly  as  possible  in  size  and 
shape  to  the  general  form  of  the  arch  and  ridge.  The  proper 
size  should  always  be  determined  by  trial  of  the  empty  cup  in 
the'mouth  before  taking  the  impression. 

Impression  cups  are  made  from  a  variety  of  substances,  as 


IMPRESSIONS    OF   THE    MOUTH.  I43 

sheet-tin,  porcelain,  vulcanized  rubber,  and  Britannia  metal,  and 
sometimes,  in  order  to  meet  the  requirements  of  special  or 
exceptional  cases,  either  brass,  copper,  block-tin,  or  gutta-percha 
may  be  used. 

Cups  constructed  of  sheet-tin,  which  any  tinner  can  readily 
make  to  order,  were  formerly  very  generally  used  for  partial 
cases,  and  if  proper  care  is  taken  not  to  inflict  injury  to  the  lips 
and  soft  parts  with  the  thin,  sharp  edges  when  introducing  and 
pressing  the  cup  to  its  place  in  the  mouth,  they  may  be  used 
with  satisfaction. 

Porcelain  cups  are  adapted  to  the  use  of  the  several  impres- 
sion materials  named,  except  plaster,  the  latter  being  quite  liable 
to  part  from  their  glazed  surfaces  on  the  application  of  the  nec- 
essary force  to  detach  the  impression,  leaving  the  plaster  in  the 
mouth.  Aside  from  their  purity  and  attractive  appearance,  they 
possess  no  advantages  that  would  make  them  preferable  to  Bri- 
tannia cups,  while  they  are  objectionable  because  of  their  liability 
to  injury,  and  entire  incapability  of  being  changed  in  form  to 
meet  special  reqiurements.  When  used  in  connection  with  wax, 
they  should  be  slightly  heated  before  the  former  is  introduced. 

Hard  rubber  trays,  of  any  desired  form,  may  be  readily  made 
from  plaster  models  by  any  one  accustomed  to  rubber  work,  and 
are  chiefly  adapted  to  the  use  of  plaster,  as  they  are  not  readily 
cleansed  if  other  plastic  substances  are  employed.  Their  form 
maybe  materially  changed  by  immersing  them  for  a  few  moments 
in  boiling  water. 

Britannia  metal,  however,  meets  most  fully  all  the  requirements 
of  an  impression  cup,  and  is  well  adapted  to  the  use  of  any  of 
the  impression  materials  commonly  employed.  The  great  vari- 
ety in  form  and  size  found  at  dental  depots  will  amply  meet  all 
the  requirements  of  ordinary  cases.  For  unusual  or  abnormal 
conditions  requiring  exceptional  forms  of  trays,  the  operator 
can  construct  for  himself,  from  these,  such  appliances  as  will 
best  serve  his  purpose  in  the  individual  case. 

The  Form  of  Cup  to  Use. — Whatever  cup  is  selected  in  secur- 
ing an  impression  in  wax  for  a  partial  upper  case,  it  should  be 
large  enough  to  embrace  the  alveolar  ridge,  leaving  a  space  of 
nearly  a  fourth  of  an  inch  between  the  rim  and  the  external  wall 


144 


MECHANICAL    DENTISTRY. 


of  the  alveolar  ridge.  In  partial  upper  cases  requiring  an 
impression,  it  may  be,  of  only  a  limited  portion  of  the  arch,  as 
where  clasps  are  used,  or  of  the  entire  hard  palate,  the  form  of 
cup  illustrated  in  Fig.  58  should  be  employed. 

A  cup  designed  for  similar  cases  by  Dr.  Wardle,  exhibited  in 
Fig.  59,  is  particularly  adapted  to  high  arches,  being  provided 
with  a  movable  palate  plate,  by  which  the  central  portion  of  the 
impression  material  is  effectually  forced  into  the  highest  portions 
of  the  palatal  arch,  and  laterally  against  the  sides  and  necks  of  the 
remainin  g  teeth.  The  same  result  can  be  accomplished,  however, 
by  using  the  ordinary  impression  cup,  and  building  up  the  rear 
and  center  of  the  palatine  portion  with  softened  beeswax,  before 
introducing  the  plaster. 

Fig.  58. 


Having  selected  a  cup  of  the  proper  form  and  size,  the  wax 
should  be  warmed  over  a  spirit  flame  until  it  acquires  about  the 
consistency  of  freshly-made  putty.  Wax  is  sometimes  softened 
by  immersing  it  in  hot  water,  but  the  dry  heat  is  preferable,  as 
the  former  seems  to  impair,  to  some  extent,  its  toughness  and 
continuity. 

The  Position  of  the  Operator. — In  taking  the  impression  the 
operator  should  place  himself  behind  and  to  the  right  of  the 
patient,  and  should  be  sufficiently  raised  above  the  latter  to  en- 
able him  to  manipulate  with  the  greatest  ease  and  certainty,  and 
at  the  same  time  to  command  as  full  and  unobstructed  a  view  of 
the  interior  of  the  mouth  as  possible. 

Manner  of  Introducing  the   Cup,  etc. — The  cup,  with  the 


IMPRESSIONS    OF    THE    MOUTH. 


145 


wax  arranged  should  then  be  introduced  into  the  mouth  with- 
out unnecessary  delay.  To  do  this  properly,  and  without  sub- 
jecting the  patient  to  annoyance,  will  occasionally  require  some 
care  and  expertness,  on  account  of  the  disproportionate  size  of 
the  cup  and  orifice  of  the  mouth.  An  ample  and  expanded  jaw, 
for  example,  is  frequently  associated  with  a  small  mouth,  and  if 
in  addition  to  this  the  sphincter  muscle  of  the  mouth  happens  to 
be  rigid  and  unyielding,  the  introduction  of  a  cup  of  sufficient 
size  may  be  attended  with  some  difficulty  and  embarrassment. 
This  impediment,  however,  may  be  readily  overcome  in  most 
cases  by  presenting  the  cup  obliquely  to  the  mouth,  one  side 
resting  against,  and  pressing  outward,  the  corner  of  the  mouth, 

Fig.  59. 


while — as  the  opposite  corner  is  extended  with  the  first  and 
second  fingers  of  the  left  hand — the  cup  is  passed  in  with  a  ro- 
tary movement. 

When  the  cup  is  within  the  mouth  it  should  be  carefully  ad- 
justed over  the  ridge  before  pressing  it  up,  so  that  no  portion  of 
the  rim  may  cut  into  the  soft  tissues  of  the  mouth,  an  accident 
liable  to  happen  without  care,  and  which  will  make  it  necessary, 
in  most  cases,  to  withdraw  the  cup  before  the  impression  is 
complete.  The  proper  position  of  the  cup  in  the  mouth  secured, 
it  should  be  held  firmly  with  the  thumb  resting  on  the  handle 
above,  and  two  or  more  of  the  fingers  on  the  under  surface, 
when  it  is  slowly  but  steadily  and  forcibly  pressed  against  the 
parts  above  until  the  ridge  is  completely  imbedded,  and  the  wax 


146  MECHANICAL    DENTISTRY. 

carried  closely  against  the  roof  of  the  mouth.  The  cup  should 
then  be  held  stationary  with  two  fingers  from  each  hand  ;  apply- 
ing equal  pressure  upon  both  sides,  while  with  the  thumbs  the 
wax  around  the  margins  of  the  cup  should  be  pressed  closely 
into  all  the  depressions  occurring  on  the  outside  of  the  ridge 
between  the  remaining  teeth,  or  wherever  irregularities  may 
present  themselves  on  the  external  border  of  the  jaw. 

After  the  wax  has  remained  in  the  mouth  long  enough  to  be- 
come in  some  degree  hardened,  it  should  be  carefully  detached 
by  gentle  traction,  upon  the  cup,  and  removed  from  the  mouth 
in  the  same  manner  in  which  it  was  introduced,  care  being 
taken  not  to  displace  the  wax  or  otherwise  mar  the  impression. 
The  force  with  which  the  wax  impression  will  adhere  to  the 
mucous  surfaces  on  the  complete  exclusion  of  air  is  oftentimes 
very  considerable,  and  will  require  a  corresponding  tractive  force 
to  dislodge  it.  In  applying  this  force,  it  should  be  borne  in 
mind  that,  in  the  very  plastic  condition  in  which  the  wax  is  ap- 
plied to  the  mouth,  it  is  not  only  very  soft  and  yielding,  bnt,  being 
zvliolly  inelastic,  is  incapable  of  recovering  its  form  when  temporarily 
disturbed,  and  that,  consequently,  any  distortion  of  the  impression 
occurring  from  the  force  applied  in  removing  it  from  the  mouth 
will  be  permanent  and  possibly  fatal.  It  should,  therefore,  as 
has  already  been  stated,  be  allowed  to  remain  in  the  mouth  long 
enough  to  become  somewhat  hardened,  say  from  three  to  five 
minutes,  and  this  process  may  be  facilitated  by  holding  against 
the  cup  a  napkin  saturated  with  cold  water.  The  proper  degree 
of  hardness  will,  however,  depend  upon  the  circumstances  of 
the  case.  If  the  remaining  teeth  present  to  each  other  parallel 
walls,  or  nearly  so,  permitting  an  easy  escape  of  the  wax  from 
the  interdental  spaces,  the  greatest  practicable  degree  of  hard- 
ness that  can  be  obtained  is  desirable.  If,  on  the  other  hand, 
these  spaces  are  V-shaped  or  dovetailed,  as  is  very  generally  the 
case  where  the  teeth  to  be  replaced  have  been  long  absent,  the  im- 
pression should  be  removed  while  the  wax  is  somewhat  plastic, 
permitting  a  ready  separation  by  such  displacement  of  wax  im- 
mediately around  the  adjoining  teeth  as  must  always  occur  in 
these  cases  in  the  use  of  wax.  In  proportion  as  the  wax  is 
rendered  hard  and  unyielding  will  be  the  resistance  to  its  escape 


IMPRESSIONS    OF    THE    MOUTH. 


147 


from  these  spaces,  and  the  danger  of  change  of  form  in  parts  of 
the  impression  more  or  less  remote  from  them  augmented.  It 
is,  therefore,  unadvisable  in  such  cases  to  produce  hardness 
artificially  by  the  application  of  ice  or  cold  water.  Under  similar 
conditions,  the  same  precaution  should  be  taken  against  over- 
hardening  in  the  use  of  modeling  composition. 

Imperfections  occurring  from  displacement  or  dragging  of 
wax  on  removal  from  the  mouth,  if  inconsiderable,  may  be 
remedied  with  tolerable  accuracy  by  subsequent  carving  of  the 
plaster  model,  and  this  may  be  aided  by  a  comparison  of  the 
plaster  representation  of  the  teeth  with  those  in  the  mouth.  If, 
however,  the  interdental  under-cuts,  and  those  associated  with 


Fig.  60. 


Fig.  61. 


bell-crowned  teeth  at  other  points,  are  more  pronounced,  it  is 
better  to  use  either  the  modeling  composition  or  plaster. 

Inasmuch  as  it  is  necessary,  in  constructing  partial  sets  of  teeth, 
where  swaged  base  plates  are  used,  to  be  provided  with  two  or 
more  plaster  models,  and  as  the  latter  cannot  well  be  obtained 
in  perfect  condition  from  a  single  impression,  it  is  better  that  at 
least  two  of  the  latter  should  be  secured  in  the  first  instance. 

Manner  of  Obtaining  an  Impression  of  the  Lower  Jaw  in 
Wax,  for  Partial  Dentures. — If  the  case  is  one  where  teeth  at 
intervals  are  to  be  supplied,  the  form  of  cup  illustrated  in  Fig. 
60  maybe  employed.  If  however,  as  is  more  generally  the  case, 
the  front  teeth  remain,  and  those  posterior  to  the  cuspids  or  bicus- 
pids are  to  be  replaced,  the  form  of  cup  exhibited  in  Fig.  61 


148  MECHANICAL    DENTISTRY. 

should  be  used,  a  portion  being  cut  out  from  the  front  part  of  it, 
forming  a  vacuity  which  receives  and  permits  an  unobstructive 
passage  of  the  front  teeth.  As  the  latter  are  often  very  long,  it 
is  difficult,  with  the  ordinary  form  of  cup,  to  press  the  wax 
down  fairly  upon  the  ridge  behind  without  bringing  their  cutting 
edges  prematurely  in  contact  with  the  floor  of  the  cup  in  front. 
Instead  of  the  opening  represented  in  the  cup,  however,  it  will  be 
sufficient  in  most  cases  to  have  it  formed  with  a  depression 
in  front  of  adequate  depth  to  receive  the  points  of  the  anterior 
teeth. 

Position  of  Operator. — In  taking  an  impression  of  the  lower 
jaw,  after  having  prepared  and  arranged  the  wax  by  softening 
and  filling  the  groove  of  the  cup  flush  with  the  margins,  the 
operator  may  first  take  a  position  to  the  right  and  back  of  the 
patient  and  introduce  the  cup  into  the  mouth  in  the  manner 
heretofore  described,  when  he  may  pass  a  little  to  the  front  of  the 
patient,  and,  having  adjusted  the  cup  properly  over  the  ridge,  he 
should  then  take  his  place  again,  at  the  side  or  back  of  the 
patient,  placing  his  fingers  of  each  hand  under  each  side  of  the 
patient's  jaw,  and  the  thumbs  upon  the  top  of  the  cup  ;  then  make 
steady  pressure  until  the  ridge  is  wholly  embedded.  Before 
final  adjustment  of  the  wax  to  the  ridge,  however,  care  should 
be  taken  not  to  enclose  any  loose  folds  of  membrane  along  the 
line  of  junction  between  the  ridge  and  cheeks,  or  of  loose  tissue 
lying  on  the  inside  near  the  base  of  the  tongue.  To  avoid  the 
former,  immediately  before  final  pressure  is  made,  the  cheek 
should  be  distended  and  drawn  outward  with  the  finger,  first  on 
one  side  and  then  on  the  other,  holding  the  cup,  in  the  mean- 
while, steadily  in  place.  The  loose  and  movable  tissues  on  the 
inside  will  be  drawn  away  from  the  ridge  somewhat  if  the  patient 
is  directed  to  raise  the  tongue  well  toward  the  roof  of  the  mouth. 
Some  little  additional  pressure  may  then  be  made  upon  the  cup, 
after  which  the  wax  should  be  pressed  in  around  the  margins  of 
the  cup,  both  externally  and  within,  when  the  impression  is 
carefully  removed  from  the  mouth,  observing  the  precautions 
stated  when  treating  of  wax  and  other  allied  substances. 

Manner  of  Obtaining  an  Impression  of  the  Mouth  in  W^ax, 
for  Entire  Upper  Dentures. — The  form  of  cup  employed  in 


IMPRESSIONS    OF   THE    MOUTH. 


149 


taking  an  impression  of  the  upper  jaw,  in  the  absence  of  all  the 
natural  teeth,  is  seen  in  Fig. 

62.     A  number  of  these  cor-  _  ^'°'  ^^■ 

responding  as  nearly  as  pos- 
sible in  form  and  size  to  the 
various  modifications  in  the 
configuration  and  dimensions 
of  the  maxillary  arch,  should 
be  kept  conveniently  at  hand. 
If  the  teeth  have  been  recently 
extracted,  the  wax  should  be 
prepared  somewhat  softer  than 
usual,  to  prevent  displacement 
of  the  gums,  which,  in  their 
unabsorbed  condition,  possess 

more  or  less  mobility.  The  cup  should  be  filled  flush  with  the 
edges,  and  built  up  in  the  center  if  the  depth  of  the  palatal  vault 
requires  it,  and  the  wax  properly  trimmed;  it  is  then  introduced 
into  the  mouth  and  adjusted  to  the  ridge,  as  already  described, 
and  pressed  to  the  ja\v  with  sufficient  force  to  fully  encase  all 
the  parts  to  which  the  substitute  is  ultimately  to  be  applied. 
The  wax,  as  the  cup  is  pressed  up,  has  a  tendency  to  roll  out  at 
its  edges  and  thus  depart  from  the  upper  and  outer  portions  of 
the  ridge ;  hence  care  must  be  taken  to  press  the  wax  in  around 
the  marginal  portions  of  the  cup,  as  has  previously  been 
directed,  filling  up  any  depressions  or  fossse  that  may  occur  on 
the  external  border  of  the  jaw.  It  is  particularly  necessary  to 
observe  this  precaution  whenever  the  ridge  overhangs,  as  is 
prominently  the  case  for  the  first  few  months  after  the  extrac- 
tion of  the  teeth. 

If  the  impression  is  an  accurate  one,  some  difficulty  is  occa- 
sionally experienced  in  detaching  it  from  the  mouth,  on  account 
of  the  thorough  exclusion  of  air  from  between  it  and  the  mouth, 
the  wax  being  held  firmly  in  place  by  adhesive  force  ;  in  which 
event  it  is  only  necessary  to  admit  the  air  between  the  two  ;  and 
this  may  generally  be  readily  effected  by  placing  the  finger 
against  the  jaw  on  one  side  and  above  the  wax,  pressing 
firmly  toward  the  center  of  the  arch  and  upward,  forcing  the 


i^o 


MECHANICAL    DENTISTRY. 


muscles  and  mucous  membrane  somewhat  from  the  edge  of  the 
cup,  and  at  the  same  time  depressing  the  latter  on  the  same 
side.  A  small  portion  of  air  being  admitted,  it  will  soon  diffuse 
itself  between  the  adhering  surfaces  and  allow  the  wax  to  be 
readily  detached. 

To  harden  the  wax,  so  as  to  prev^ent  it  from  dragging  at  the 
points  where  the  ridge  overhangs,  or  to  prevent  any  change  in 
its  shape  on  the  application  of  sufficient  force  to  detach  it  from 
the  mouth,  apply  to  the  cup,  for  several  minutes,  a  small  napkin 
saturated  with  ice-cold  water,  or  enclosing  a  piece  of  ice. 

The  writer  would  repeat,  in  this  connection,  his  conviction  that 
it  is  impracticable,  in  most  cases,  to  obtain  a  faultless  impression 
of  the  mouth  in  wax.  There  are  points,  not  readily  accessible 
to  the  fingers,  where  the  wax  departs  from  the  external  and  pos- 
terior borders  of  the  jaw,  and  is  not,  therefore,  susceptible  of  easy 
correction ;  besides,  when  reached  and  the  remedy  applied,  there 
is  no  certain  assurance  that  in  pressing  the  wax  in  at  one  point 
we  are  not  displacing  it  at  another.  The  same  uncertainty,  to 
a  less  degree,  in  regard  to  results  also  attaches  to  the  use  of  the 
modeling  composition.  For  this  reason,  we  almost  invariably 
use  plaster,  and  we  have  sufficient  reason  to  believe  that  the 
results  are  more  uniformly  successful. 

Manner  of  Obtaining  an  Impression  of  the  Lower  Jaw  in 

— The  method  pursued  in  securing 
an  impression  of  the  lower  jaw  in 
wax  for  an  entire  denture  differs 
in  no  essential  respect  from  that 
described  when  taking  an  impres- 
sion for  lower  partial  pieces,  the 
form  of  cup  being  represented  in 
Fig.  63.  When  the  parts  are  im- 
bedded in  the  wax,  the  latter  should 
be  pressed  in  around  the  inner  bor- 
der of  the  holder,  but  more  especial- 
ly near  the  posterior  part  of  the  ridge 
on  each  side  where  the  latter  over- 
hang and  approximate  each  other, 
forming  corresponding  excavations  underneath.      After  adjust- 


Wax,  for  Entire  Dentures. 

Fig.  6.;. 


-^ 


IMPRESSIONS    OF    THE    MOUTH.  I5I 

ing  the  wax  to  the  ridge  along  the  border  of  the  cup,  the  latter 
should  again  be  pressed  directly  down  upon  the  jaw  before 
removing  it,  to  correct  any  partial  deformity  that  may  have 
occurred  during  the  previous  manipulations. 

Modeling  Composition,  of  late  years  has  largely  superseded 
the  use  of  wax  for  impressions.  It  is  compounded  of  gum 
dammar,  stearin,  French  chalk,  carmin  for  coloring,  and  some 
perfume.  The  consistence  of  the  mass  depends  upon  the  rela- 
tive quantity  of  stearin  and  chalk  introduced,  the  grades  as 
manufactured  being  designated  as  soft,  medium,  and  hard. 

This  material  takes  a  sharper  impression  of  the  parts  than 
wax,  and  its  elastic  property  makes  it  more  suitable  where 
there  are  overhanging  ridges,  irregularly  arranged  and  bell- 
crowned  teeth,  and  dovetailed  interdental  spaces.  It  is  prepared 
for  use  by  softening  it  either  with  dry  heat,  or  by  immersing  it 
in  hot  water.  When  sufficiently  plastic,  it  is  introduced  into  a 
cup  slightly  heated  to  render  the  material  somewhat  adhesive, 
and  then  placed  in  the  mouth  as  has  been  directed  for  wax 
impressions. 

Before  removing  it  from  the  mouth,  it  should  be  cooled  some- 
what in  order  to  preserve  its  form  unchanged.  Excessive  hard- 
ness, however,  should  be  avoided  where  portions  are  pressed 
into  unusual  undercut  spaces,  as  the  force  necessary  to  detach  it 
in  such  cases  may  produce  deformity  of  the  body  of  the  impres- 
sion more  or  less  remote  from  the  teeth  and  spaces  mentioned. 
When  removed  it  should  be  immediately  dipped  in  cold  water. 
The  general  manipulation  of  the  compound  in  the  mouth,  both  in 
full  and  partial  cases,  is  the  same  as  that  described  when  wax  is 
used,  and  the  same  care  should  be  observed  when  removing  the 
impression  from  the  mouth. 

Moldine. — This  plastic  compound,  originated  by  Dr.  George 
W.  Melotte,  and  used  by  him  chiefly  in  connection  with  crown 
and  bridge  work,  is  composed  of  potter's  clay  mixed  with  glycerin 
to  the  consistency  of  stiff  putty.  With  the  observance  of  certain 
precautions  in  the  use  of  this  material,  the  operator  is  enabled 
very  quickly  to  secure  a  metallic  die  and  counter-die  immedi- 
ately from  the  impression. 

The  following,  in  substance,  is  Dr.  Melotte's  method  of  using 


152 


MECHANICAL    DENTISTRY. 


it  and  of  obtaining  the  die  and  counter-die.  Make  the  tooth  or 
teeth  perfectly  dry,  and,  filhng  the  cup  (Fig.  64)  nearly  full  with 
moldine,  coat  it  with  soap-stone  powder,  and  take  the  impression 
in  the  usual  manner.  Carefully  remove  the  cup ;  trim  off  any 
overhanging  material,  and  place  the  rubber  ring  (Fig.  65)  over  the 
cup  to  about  one-half  the  depth  of  the  ring.  Melt  the  fusible 
metal  and  pour  it  as  cool  as  it  will  run  from  the  iron  ladle.  As 
soon  as  the  metal  is  hard,  remove  it  with  the  ring,  taking  care 
not  to  impair  the  impression,  which  can  be  used  again  if  the  die 
is  found  imperfect  or  is  injured  in  use.  Place  the  die  and  ring 
in  cold  water,  to  remain  until  quite  cooled.  While  the  die  is  wet 
and  held  over  a  basin  of  water,  pour  into  the  ring  fusible  metal 
which  has  been  stirred  until  it  begins  to  granulate,  and  quickly 


Fig.  64. 


Fig.  61;. 


immerse  all  in  the  water.  The  die  and  counter-die  should  sepa- 
rate readily  by  tapping  them  with  a  hammer,  but  if  they  stick, 
others  can  be  quickly  made  from  the  same  impression,  by  the 
same  method,  using  more  care. 

Plaster-of-Paris. — Plaster-of-Paris,  or,  technically,  calcium 
sulphate,  has  been  long  employed  in  taking  impressions  of 
the  mouth  for  entire  dentures,  and  of  late  years  it  has  almost 
entirely  superseded  the  use  of  all  other  materials,  on  account  of 
its  capability  of  receiving  a  practically  faultless  imprint  of  the 
parts  on  which  the  substitute  rests.  The  same  quality  of  exact- 
ness recommends  it  also  in  partial  cases  where  conditions  exist 
that  render  an  accurate  impression  of  the  parts  with  other  ma- 
terials impossible. 

Derivation. — Plaster  is  derived  from  gypsum  by  a  process  of 


IMPRESSIONS    OF    THE    MOUTH.  1 53 

calcination.  The  latter,  or  gypsum,  is  a  common  mineral,  fre- 
quently crystallized,  oftener  amorphous,  and  oftentimes  forming 
rock  masses.  Its  transparent  variety,  called  selenite,  sometimes 
occurs  in  large  plates,  which  have  been  used  for  windows.  It 
also  frequently  occurs  in  aggregated  needle-like  crystals,  and  is 
then  called  fibrous  gypsum.  In  its  amorphous  condition,  when 
compact  and  translucent,  it  is  named  alabaster.  More  com- 
monly it  is  white,  opaque,  and  soft,  and  is  then  called  snowy 
gypsum.  The  most  important  deposits  known  are  those  of  the 
Paris  basin  at  Montmartre,  from  which  it  has  taken  the  common 
name  of  plaster-of-Paris. 

Manner  of  Preparing. — In  the  preparation  of  plaster,  as 
used  in  the  arts,  the  gypsum  rock  is  ground  between  burstones 
until  it  is  reduced  to  a  fine  powder,  when  it  is  calcined  by  being 
heated  in  kettles  or  stills,  the  combining  water  being  thus 
driven  off.  If,  in  this  condition,  it  is  again  mixed  with  water, 
the  latter  recombines  with  it,  the  mass  becoming  first  plastic, 
and  then  solid.  Hence,  it  is  admirably  adapted  to  a  great  variety 
of  modeling  processes.  In  its  ordinary  calcined  form,  plaster  ab- 
sorbs moisture  from  the  2i\.vnos^]\e:ve, and  shojdd,  therefore,  be  care- 
fully protected  froin  dampness.  Should  the  latter  occur,  however, 
the  uncom.bined  moisture  may  be  driven  off  by  exposing  the  plas- 
ter to  a  moderate  heat  in  a  shallow  pan  or  other  suitable  vessel. 

In  the  process  of  hardening,  after  having  been  made  plastic  by 
the  addition  of  v\^ater,  more  or  less  expansion  of  the  mass,  both 
during  and  for  a  time  after  solidification,  takes  place,  varying 
with  the  kind  of  plaster  used  and  the  various  methods  employed 
in  preparing  it  for  molding  purposes. 

To  Hasten  the  Setting  of  plaster  use  warm  water  for  mix- 
ing, or  add  about  ten  grains  of  common  salt  (sodium  chlorid)  to 
the  water  before  introducing  the  plaster,  when  about  to  take  an 
impression.  The  salt  also  makes  the  plaster  more  brittle,  which 
is  desirable  in  impressions.  It  is  better  to  add  the  salt  before 
the  plaster,  as  it  gives  it  a  better  opportunity  to  become  uni- 
formly diffused.  Other  agents,  such  as  chlorate  of  potash, 
potassium  sulphate,  and  alum,  have  been  and  are  used  to  hasten 
the  setting  of  plaster;  but  salt  is  the  least  objectionable  and 
answers  every  purpose. 


154  MECHANICAL    DENTISTRY. 

Manner  of  Obtaining  an  Impression  of  the  Mouth  in 
Plaster,  for  Partial  Upper  and  Lower  Dentures. — In  partial 
cases,  whether  above  or  below,  there  are,  almost  universally, 
conditions  associated  with  the  presence  of  the  remaining  natural 
teeth  which,  until  more  recently,  have  been  thought  to  contra- 
indicate  the  use  of  plaster  as  an  impression  material,  but  experi- 
ence has  demonstrated  that,  with  the  adoption  of  certain  available 
means  and  careful  and  skilful  manipulation,  there  are  few  if  any 
cases  in  which  this  material  may  not  be  successfully  employed. 
Its  superior  capabilities  of  receiving  a  faultless  imprint  of  the 
mucous  surfaces  recommend  it  for  this  purpose  in  all  suitable 
cases. 

The  conditions  mentioned  above  relate  to  those  cases  where 
the  cervical  portions  of  the  crowns  are  relatively  small ;  or  where 
the  teeth  are  irregularly  arranged  in  the  circle,  having  either  an 
anterior,  posterior,  or  lateral  obliquity ;  or  where  there  are 
marked  depressions  or  fossae  on  the  external  border  of  the 
alveolar  ridge;  and  especially  where  there  are  well-defined  dove- 
tailed or  wedge-shaped  interdental  spaces.  These  conditions 
prevail  in  different  degrees  in  individual  cases,  and  the  instances 
are  exceedingly  rare  where  some  or  all  of  them  are  not  present. 
As  plaster  prepared  for  impressions,  in  the  act  of  setting  or 
hardening,  becomes  rigid  and  unyielding,  and  therefore  prac- 
tically incapable  of  any  change  of  form  by  distortion  or  dragging 
of  any  portion  of  it  on  traction,  the  difficulty,  not  to  say 
impossibility,  of  detaching  it  by  the  ordinary  means,  where  these 
conditions  prevail,  will  be  apparent.  In  cases  of  very  slight 
deviation  from  the  normal  position  of  the  teeth,  sufficient  force, 
judiciously  applied,  will  disengage  the  impression,  provided  the 
plaster  is  not  allowed  to  set  hard. 

If  the  mal-arrangement  of  the  teeth  is  considerable,  or  very 
pronounced,  the  separation  of  the  plaster  impression  must  be 
accomplished  in  some  other  way  than  by  simple  traction.  Prof. 
Charles  J.  Essig  recommends  the  following  method  of  pro- 
cedure : — 

"An  impression  cup  should  first  be  selected  of  the  proper  size 
and  shape — those  with  the  flat  floor  (Fig.  58)  are  best  for  partial 
cases  ;  the  plaster  should  be  mixed  quite  thin,  adding  chlorid 


IMPRESSIONS    OF    THE    MOUTH.  1 55 

of  soda  to  facilitate  setting.  Plaster  mixed  in  this  manner  does 
not  become  so  hard  and  unyielding  as  that  mixed  merely  to 
saturation.  Now  oil  the  cup  so  that  it  will  readily  separate 
from  the  impression  when  hard,  fill  the  cup  as  soon  as  the 
plaster  thickens  sufficiently,  then,  with  a  small  spatula,  place  a 
layer  of  the  soft  plaster  in  upon  the  palatine  surface,  otherwise, 
by  enclosing  the  air  in  the  deep  portion  of  the  arch,  the  accuracy 
of  the  impression  may  be  impaired.  After  this  precaution,  the 
cup  is  placed  in  the  mouth,  and  gently  pressed  up  until  its  floor 
comes  in  contact  with  the  teeth.  When  the  plaster  is  sufficiently 
hardened,  remove  the  cup,  which,  froni  its  having  been  oiled,  is 
done  without  difficulty  ;  with  the  thumb  and  index  finger  break 
off  the  outside  walls  ;  the  portion  covering  the  palatine  surface 
is  then  removed  by  the  use  of  a  blunt  steel  spatula,  curved  at  the 
end  in  the  form  of  a  hook.  The  pieces  are  then  placed  back  into 
the  cup,  where  they  will  be  found  to  articulate  with  perfect 
accuracy. 

"  Should  the  first  attempt  be  rendered  futile,  by  the  tendency 
to  nausea  or  troublesome  gagging  on  the  part  of  the  patient* 
camphor  water,  as  recommended  by  Dr.  Louis  Jack,  may  be 
used  as  a  gargle,  which  will,  in  nearly  every  case,  prove  an 
effectual  remedy." 

This  device  is  effectual  to  the  extent  described  by  Prof  Essig, 
but  it  affords  only  a  partial  remedy  for  difficulties  which  present 
themselves  in  many  of  these  cases.  The  most  formidable  obstacle 
to  the  removal  of  a  plaster  impression  will  be  found  generally  in 
that  portion  of  it  embraced  in  wedge-shaped  interdental  spaces, 
and  undercuts  formed  by  truncated,  cone-shaped  crowns,  and 
malpositions  of  the  teeth  ;  and  when  the  outside  walls  of  the 
impression  alone  are  broken  off,  and  remaining  portions  are 
imbedded  in  these  undercuts,  it  will  rarely  be  possible  to  remove 
the  portion  covering  the  palatal  surface  without  further  fracture 
and  removal  by  sections. 

The  author  is  indebted  to  Prof  Wilbur  F.  Litch  for  the  follow- 
ing description  and  illustration  (Fig.  66)  of  a  method  of  securing 
piaster  impressions  for  partial  cases  : — 

"  A  wax  impression  tray  is  made,  and  either  scored  or  perfor- 
ated, to  afford  anchorage  for  the   plaster.     This    extends  only 


156  MECHANICAL    DENTISTRY. 

midway  of  teeth  or  interspace.  After  the  plaster  has  hardened, 
the  outer  edge  is  trimmed,  notched,  and  oiled  in  the  mouth,  and 
sections  D  D  of  the  diagram  made  by  carrying  plaster  into  posi- 
tion by  means  of  a  spatula,  the  outer  section  being  made  in  two 
pieces,  joined  at  about  the  median  line.  The  three  pieces  are 
removed  separately  and  joined  by  means  of  the  notches  made 
in  the  palatine  section  C,  into  which  notches  the  plaster  of 
sections  D  D  will  fit.  After  the  three  sections  are  cemented 
together,  they  may  be  embedded  in  plaster,  to  more  securely 
hold  them  together  while  the  model  is  being  poured." 

Another  method  of  securing  plaster  impressions  in  sections  is 
the  following,  suggested  by  Dr.  A.  G.  Bennett: — 

"A  wax  cut-off  is  placed  in  the  floor  of  the  impression  tray 

Fig.  66. 


A  A.  Teeth  or  interspace.  B.  Wax  impression  tray.  C.  Plaster  impression  of  pala- 
tine vault  and  palatal  half  of  teeih  or  interspace.  D  D.  Buccal  or  labial  half 
of  teeth  or  interspace.     E.   Palatal  vault. 

in  such  manner  that  it  will  touch  the  crowns  of  the  molars  and 
the  cutting  edges  of  the  incisors  about  midway  between  their 
buccal  or  labial  and  palatine  walls,  as  shown  in  Fig.  67,  letters 
D  D.  After  the  wax  cut-offs  have  been  firmly  attached  to  the 
tray  by  heat,  the  tray  is  oiled,  filled  with  plaster,  and  placed  in 
position  in  the  mouth.  After  the  plaster  has  hardened,  the  tray 
is  withdrawn,  the  plaster  remaining  in  the  mouth,  when  the  outer 
sections,  E  E,  are  readily  broken  off,  and  the  plaster  section,  F, 
withdrawn.  The  several  pieces  are  then  replaced  in  their  proper 
position  in  the  tray." 

Another  method  of  procedure  in  the  class  of  cases  under  con- 
sidei-ation  is  that  described  by  the  late  Dr.  F.  M.  Dixon,  of 
Philadelphia,  which    seems    to    provide   more    perfectly  for  the 


IMPRESSIONS    OF    THE    MOUTH.  1 57 

remov^al  of  the  palatal  portion  of  the  impression  in  cases 
characterized  by  unusual  inward  inclination  of  the  teeth.  The 
process  described  relates  to  partial  upper  cases  : — 

"  First  take  an  impression  of  the  whole  upper  jaw  in  wax,  and 
harden  by  applying  ice-water.  Divide  this  impression,  with  a 
slightly  heated  knife  blade,  into  the  number  of  sections  desired 
for  the  plaster  impression.  From  the  inner  surfaces  of  these 
sections,  a  sufficient  quantity  of  the  wax  is  cut  away  to  make 
room  for  the  required  amount  of  plaster.  Flard-setting  plaster 
is  then  poured  into  one  of  the  palatal  sections,  and  the  latter 
placed  in  its  proper  position  in  the  mouth,  securing  an  impres- 
sion of  the  palatal  surfaces  of  the  teeth  of  that  side,  and  about 
one-third  of  the  palate  of  the  same  side.     When  the  plaster  has 

Fig.  67. 


A  A.  Molar  teeth.  .  B.  Palatine  vault.  CCC.  Impression  tray.  D  D.  Wax  cut- 
offs. E  E.  Labial  sections  of  plaster  impressions.  P".  Palatal  section  of  im- 
pression. 

hardened  sufficiently,  the  section  is  removed  and  laid  to  one  side 
while  an  impression  of  the  opposite  side  is  secured  in  the  same 
manner. 

"  The  patient  may  now  be  dismissed  with  an  appointment  for 
another  sitting.  In  the  interim,  these  sections  are  carefully 
trimmed  in  such  a  manner  that  the  lower  or  lingual  surface  shall 
present  a  bevel  from  margins  near  the  mesial  line  of  the  palate 
to  the  grinding  surfaces  of  the  teeth,  that  the  next  section  may 
be  readily  removed  after  the  hardening  in  the  mouth.  When 
the  patient  returns,  the  prepared  lateral  sections,  oiled  on  their 
under  surfaces,  are  placed  in  the  mouth  and  an  impression  of 
the  central  portion  of  the  palate  and  palatal  surfaces  of  the 
incisors  is  secured    as  before.      The  impressions  of  the  buccal 


158  MECHANICAL    DENTISTRY. 

surfaces,  when  needed,  are  taken  in  like  manner,  with  the  other 
sections  in  situ." 

Manner  of  Obtaining  an  Impression  of  the  Mouth  in 
Plaster  for  Entire  Upper  Dentures. — The  form  of  cup  used 
in  securing  an  impression  of  the  upper  jaw  for  entire  sets  of 
teeth  differs  in  no  essential  respect  from  that  recommended 
when  wax  is  used  for  similar  purposes  (Fig.  62).  If  the  external 
border  of  the  alveolar  ridge  is  very  deep,  or  there  is  considerable 
space  intervening  between  the  heel  of  the  cup  and  the  floor  of  the 
palate,  a  rim  of  wax  should  be  placed  across  the  posterior  border 
of  the  cup,  to  carry  the  plaster  well  up  at  this  point,  so  as  to 
secure  ah  accurate  impression,  and  to  more  effectually  confine 
the  plaster  within  the  cup  and  prevent  its  escape  into  the  back 
part  of  the  mouth  before  it  has  fairly  reached  the  palatal  vault. 
If  the  latter  is  extremely  deep,  with  a  marked  excavation  in  its 
central  and  anterior  portion,  or  if  it  presents  somewhat  the  form 
of  a  deep  fissure,  the  plaster  may  fail  to  be  carried  perfectly 
against  the  floor  of  the  palate,  or  the  air,  becoming  confined 
within  the  central  portion  of  the  arch,  when  the  plaster  is  pressed 
up,  may  displace  the  latter  and  form  corresponding  chambers  in 
the  impression.  If  these  imperfections  are  but  slight,  they  may 
be  subsequently  remedied  either  by  filling  up  the  cavity  or  cavi- 
ties in  the  impression,  or  by  trimming  away  at  these  points  from 
the  model.  The  better  plan,  however,  where  these  conditions  of 
the  vault  prevail,  is  to  take  up  a  small  portion  of  plaster  on  the 
end  of  a  spatula  and  apply  it  to  the  deeper  portions  of  the  arch 
just  before  introducing  the  cup.  In  preparing  plaster  for  use  in 
these  cases,  it  should  be  so  treated  as  to  insure  quick  setting 
when  applied  to  the  mouth.  This  is  generally  accomplished 
either  by  adding  to  a  very  thin  mixture  of  plaster  and  water  a 
small  quantity  of  sodium  chlorid  or  common  salt  and  stirring 
until  it  begins  to  thicken.  It  then  adapts  itself  readily  to  the 
parts,  hardens  quickly,  and  is  not  liable,  with  ordinary  care,  to 
incommode  the  patient  by  running  back  too  far  upon  the  soft 
palate  or  into  the  fauces.  So  quickly,  indeed,  does  it  condense, 
that  unless  expeditiously  introduced  into  the  mouth,  it  will 
begin  to  "  set "  before  the  parts  are  fairly  embedded.  When 
preparing   it  for   use,  therefore,  the  plaster  should  be  mixed  at 


IMPRESSIONS    OF    THE    MOUTH.  1 59 

the  chair  with  the  cup  conveniently  at  hand,  while  the  patient 
should  be  in  proper  position  and  in  immediate  readiness  for 
the  operation. 

In  view  of  the  liability  of  the  plaster  to  run  back  into  the 
fauces  when  the  cup  is  pressed  to  its  place  in  the  mouth,  pro- 
ducing nausea  and  involuntary  retching,  and  which  is  very  liable 
to  occur  whenever  the  mixture  is  too  thin  or  is  improperly 
manipulated,  it  is  recommended  to  instruct  the  patient  to  avoid 
swallowing  while  the  plaster  is  in  the  mouth,  and  to  breathe 
entirely  through  the  nostrils,  which  act  keeps  the  mouth  and 
throat  quiet,  and  hence  less  liable  to  irritation  from  the  impres- 
sion material  and  the  accumulation  of  saliva  in  the  mouth. 

Position  of  Patient,  etc. — The  patient  being  seated  as  nearly 
upright  in  the  chair  as  possible,  with  the  head  inclined  slightly 
forward,  the  cup  is  filled  with  the  plaster  mixture  and  introduced 
quickly  into  the  mouth,  when  it  is  pressed  up  slowly  and  gently 
(the  rear  or  heel  of  the  cup  first,  which  causes  most  of  the  sur- 
plus plaster  to  be  forced  forward),  until  the  parts  are  completely 
encased  and  portions  of  plaster  are  seen  to  protrude  from  all  parts 
of  the  margins  of  the  cup,  otherwise  the  impression  is  liable  to 
be  imperfect,  either  on  its  outer  borders  or  on  its  posterior  palatal 
face.  Immediately  after  introducing  and  pressing  up  the  cup,  the 
lip  in  front  should  be  extended  and  drawn  down  over  the  cup,  when 
gentle  pressure,  as  the  plaster  is  hardening,  may  be  made  upon 
the  lip  and  cheeks,  to  force  the  plaster  more  perfectly  into  close 
contact  with  the  outer  surface  of  the  alveolar  ridcfe. 

It  is  essential  to  perfect  success  in  this  operation  that  the  cup, 
after  the  parts  are  once  embedded,  should  be  held  perfectly  sta- 
tionary until  the  plaster  becomes  fixed,  as  the  slightest  movement 
when  the  plaster  is  in  the  act  of  consolidating  will  derange  the 
impression  and  render  it  faulty.  Again,  if  after  the  parts  are 
embedded  the  operator  discovers  that  they  are  not  sufficiently 
encased,  and  the  plaster  has  partially  set,  no  further  effort  should 
be  made  to  press  the  plaster  up  upon  the  parts,  but  the  cup 
should  be  withdrawn  and  the  operation  repeated  with  fresh 
plaster. 

If  the  operation  has  been  successfully  conducted,  the  plaster 
will  adhere  to  the  mouth,  in  most  instances,  with  great  tenacity, 


l6o  MECHANICAL    DENTISTRY. 

and  it  will  be  necessary  to  observe  some  caution  in  removing  it, 
for,  if  forcibly  detached,  injury  may  be  inflicted  upon  the  soft 
parts  by  tearing  away  portions  of  mucous  membrane  ;  or  the 
impression  may  be  badly  fractured  or  otherwise  impaired.  In 
addition  to  the  means  already  alluded  to  in  connection  with  the 
method  of  separating  wax  impressions  from  the  mouth,  resort  is 
sometimes  had  to  the  following  expedient:  The  central  portion 
of  the  cup  being  pierced  with  two  or  three  small  holes,  a  blunt- 
pointed  probe  is  passed  at  these  points  through  the  plaster,  be- 
fore the  latter  has  hardened  perfectly,  to  the  roof  of  the  mouth. 
Into  these  passages  the  external  air  passes  and  diffuses  itself 
between  the  surface  of  the  plaster  and  the  palate,  when  the 
impression  may  be  readily  detached.  The  writer,  however,  has 
succeeded  best  in  detaching  impressions  in  such  cases  by  upward 
and  interrupted  traction  upon  the  handle  of  the  cup,  which,  by 
depressing  the  latter  posteriorly,  more  readily  permits  the  intro- 
duction of  air  than  by  either  of  the  methods  commonly  employed. 

Manner  of  Obtaining  an  Impression  of  the  Mouth  in 
Plaster,  for  Entire  Lower  Dentures. — The  general  form  of  cup 
used  for  the  above  purpose  is  shown  in  Fig.  63.  This  being 
filled  with  the  plaster  mixture,  prepared  as  described  in  connec- 
tion with  full  upper  pieces,  is  inverted  and  quickly  introduced 
into  the  mouth  and  pressed  down  upon  the  ridge  until  the  latter 
is  completely  embedded,  being  careful  at  the  same  time  to  draw 
the  lower  lip  away  from  the  cup,  and  the  cheeks  outward,  in 
order  to  prevent  any  loose  tissues  from  folding  in  upon  the  outer 
borders  of  the  ridge  as  the  cup  is  pressed  to  place,  thus  seriously 
marring  the  impression. 

It  is  thought  by  many  operators  that  better  results  can  be 
secured  by  first  taking  the  impression  in  wax,  enlarging  the 
impression  thus  secured  with  suitable  instruments,  and  using  this 
as  a  tray  for  plaster. 


CHAPTER  III. 
PLASTER  MODELS. 

After  an  impression  of  the  mouth  has  been  secured  in  either 
of  the  ways  mentioned  in  the  preceding  chapter,  the  next  step 
in  the  process  of  constructing  an  artificial  denture  is  to  procure 
from  the  impression  a  representation  of  the  parts  in  plaster. 
The  copy  thus  secured  is  called  a  model,  or  cast,  and  if  cor- 
rectly obtained  is  a  true  counterpart  or  fac-simile  of  all  parts  of 
the  mouth  represented  in  the  impression. 

Manner  of  Obtaining  a  Plaster  Model  from  an  Impression 
in  Wax  or  Modeling  Compound,  for  Partial  Dentures. — 
The  impression  should  be  first  trimmed  by  cutting  away  super- 
fluous portions  that  overhang  the  borders  of  the  cup,  care 
being  taken  not  to  mar  any  essential  part  of  the  impression.  The 
surface  imprinted  should  then  be  uniformly  and  thinly  coated 
with  soapy  water  or  oil,  applied  with  a  camel's-hair  brush.  This 
should  not  be  of  too  thick  a  consistency,  nor  applied  in  too 
large  quantities,  as  it  will  collect  in  the  more  depending  portions 
of  the  impression,  and,  failing  to  be  displaced  by  the  plaster,  leave 
the  model  imperfect  at  these  points,  especially  at  the  coronal 
extremities  of  the  plaster  teeth.  The  cup  is  now  surrounded  by 
some  substance  that  will  confine  the  plaster  and  give  proper 
form  to  the  body  of  the  model.  For  this  purpose  any  material 
that  is  easily  shaped  may  be  used,  as  a  thin  sheet  of  lead  or  wax, 
paper,  strips  of  oil  or  wax  cloth,  etc. 

Before  pouring  the  plaster,  if  it  is  desired  to  strengthen  any 
of  the  plaster  teeth — as  those  adjoining  the  vacuities  in  the  jaw, 
or  such  as  are  to  be  used  in  adjusting  clasps — and  thus  secure 
them  against  accident  in  handling,  adequate  support  may  be 
imparted  to  them  by  placing  short  pieces  of  stiff  wire  vertically 
in  the  depressions  made  in  the  impression  by  the  teeth,  support- 
ing them  in  an  upright  position  by  embedding  one  end  in  the 
wax  or  other  material  in  the  center  of  the  bottom  of  each  cavity. 
11  i6i 


l62  MECHANICAL    DENTISTRY. 

When  the  cup  is  properly  inclosed,  a  batter  of  plaster,  ot 
somewhat  thinner  consistency  than  that  used  for  impressions,  is 
poured  in  upon  the  surface  of  the  wax  in  sufficient  quantity  to 
give  to  the  body  of  the  model  a  depth  of  from  one  to  three  inches, 
according  to  the  particular  requirements  of  the  case.  The 
plaster  should  not  be  poured  directly  or  hastily  into  the  cavities 
formed  by  the  teeth,  but  upon  points  contiguous  to  them,  and 
from  which  it  should  be  allowed  to  run  slowly  into  the  depres- 
sions, by  tapping  the  bottom  of  the  cup  gently  upon  the  table, 
thus  expelling  the  contained  oil  or  air,  and  filling  them  perfectly. 
When  the  plaster  has  become  sufficiently  hard,  any  portions 
overlapping  the  borders  of  the  impression,  and  not  essential  to 
the  form  of  the  model,  should  be  cut  away,  and  the  two  separated 
by  immersion  in  warm  water  until  the  warmth  imparted  to  the 
model  renders  the  impression  sufficiently  soft  to  allow  the  former 
to  be  removed  without  fracturing  the  plaster  teeth. 

The  general  form  of  the  body  of  a  model  is  shown  in  Fig.  69. 
Where  a  swaged  base  is  required,  the  walls,  as  will  be  seen,  are 
made  as  nearly  vertical  or  parallel  as  will  admit  of  the  model 
being  readily  detached  from  the  sand  in  the  process  of  molding; 
for  if  made  too  flaring  or  divergent,  the  metallic  die  obtained 
from  it  will  be  more  liable  to  crack  or  spread  apart  under  the 
repeated  strokes  of  a  heavy  hammer,  or  to  rock  under  one-sided 
blows. 

During  the  process  of  stamping  or  forcing  a  metallic  base  into 
adaptation  to  the  die — which  is  a  metallic  counterpart  of  the  model 
— the  plate,  when  cut  to  the  exact  pattern  of  the  parts  to  be 
covered  by  it,  is  frequently  forced  or  dragged  back  toward  the 
heel  of  the  die,  and  is  thus  drawn  from  the  teeth  at  the  sides 
and  in  front.  This  displacement  of  the  plate  may  be  prevented 
by  cutting  away  all  of  the  plaster  teeth  from  the  model,  leaving, 
however,  enough  of  them  remaining  where  they  unite  with  the 
body  of  the  model  to  form  a  shoulder  to  each  tooth,  as  in  Fig. 
68.  In  this  case  the  plate  should  be  sufficiently  ample  in  its 
dimensions  to  partially  overlap  the  border,  when,  as  it  is  forced 
into  adaptation,  distinct  indentations  will  be  made  in  it,  corres- 
ponding exactly  with  the  palatal  curvatures  of  the  teeth ;  the 
portions  of  the  plate  covering  the  cut  ends  of  the  teeth  are  then 


PLASTER    MODELS. 


163 


Fig.  68. 


cut  away  with  plate  forceps  or  other  instruments.  If,  how- 
ever, the  plate  is  of  the  exact  size  required  before  stamping,  one 
or  two  plaster  teeth  upon  each  side  of 
the  model  may  be  allowed  to  remain, 
against  the  anterior  face  of  Avhich  the 
plate  is  made  to  rest,  holding  it  sta- 
tionary. 

Manner  of  Obtaining  a  Plaster 
Model  from  an  Impression  in  Wax 
or  Modeling  Compound,  for  Entire 
Dentures. — The  same  general  meth- 
od is  pursued  in  obtaining  a  plaster 
model  from  an  impression  of  either 
the    upper    or    lower   jaw   for    entire 

dentures  with  the  substances  mentioned,  as  that  employed  in 
partial  cases.  The  general  form  of  these  pieces  is  represented 
in  Figs.  69  and  70. 

If  it  is  desired  to  swage  a  rim  to  the  plate,  forming  a  groove 
or  socket  into  which  the  plate  extremities   of  the  teeth  are  re- 


FlG.  69. 


Fig.  70. 


ceived,  the  model  should  be  formed  in  the  manner  represented 
in  the  annexed  cuts  ;  in  which  it  will  be  seen  that  an  abrupt 
shoulder  is  formed  on  the  external  border  of  the  model  of  the 
upper  jaw  (Fig.  69),  but  which  on  the  lower  (Fig.  70)  is  extended 
round  the  inner  border  also,  as  it  is  desirable,  in  the  latter  case, 
to  give  a  rounded  edge  to  the  lingual  border  of  the  plate,  and 
which  is  accomplished  in  part  by  swaging  in  the  first   instance 


164  MECHANICAL    DENTISTRY. 

and  afterward  by  turning  the  edge  down  upon  the  plate  with 
pliers  or  by  other  means.  The  model  is  prepared  by  adjusting 
a  strip  of  softened  wax  around  the  border  and  cutting  away  from 
its  upper  surface  in  such  a  way  as  to  forma  groove,  the  bottom  of 
which  shall  be  -on  a  line  with  the  extreme  edge  of  the  base  or 
plate,  which  should  be  indicated  upon  the  model  with  a  pencil 
mark  before  applying  the  roll  of  wax. 

Rimmed  plates,  however,  are  only  required  when  single 
gum  teeth  or  sectional  or  entire  blocks  are  employed,  or  when 
plate  teeth  are  mounted  on  a  platinum  base  with  continuous 
gum. 

Forming  the  Air  Chamber. — Whenever  an  air  chamber  is 
to  be  stamped  in  the  base,  the  model  should  be  prepared  for  the 
purpose  before  casting  the  metallic  swages.  The  general  form 
and  position  of  the  central  cavity  or  chamber  in  the  arch  is 
represented  in  Fig.  69.  The  model  may  be  prepared  in  either 
of  the  following  ways:  i.  The  form  of  the  chamber  may  be  cut 
from  the  wax  or  plaster  impression,  in  which  case  the  plaster 
will  be  raised  at  a  corresponding  point  or  points  upon  the  model, 
and  will  have  exactly  the  same  form  and  depth  as  the  cavity  in 
the  impression.  2.  Cover  the  palatal  face  of  the  model  with  a 
sheet  of  wax  equal  in  thickness  to  the  required  depth  of  the 
chamber,  and  cut  out  from  this,  at  the  desired  point,  the  form  of 
the  cavity  ;  fill  the  latter  with  plaster,  and  when  hard  remove 
the  wax  and  trim  the  raised  portion  to  the  proper  form.  3. 
Cut  a  pattern,  of  the  required  form  and  depth  of  chamber,  from 
sheet  wax  or  lead  ;  place  it  in  proper  position  in  the  arch,  and 
press  down  with  the  fingers  or  burnisher  until  it  conforms  to 
the  contour  of  the  palate  ;  it  is  then  fixed  in  place  either  by 
confining  it  with  a  small  pin  or  tack  driven  through  it  into 
the  plaster,  or  by  interposing  softened  wax  or  other  adhesive 
material  between  the  pattern  and  model.  A  small  brush  loaded 
with  a  varnish  mixture  passed  around  the  edge  of  the  pattern 
will  insure  sufficient  adhesion  of  the  latter. 

The  same  general  method  as  that  when  central  chambers  are 
formed  is  pursued  in  the  preparation  of  the  model  when  it  is 
desired  to  construct  lateral  cavities  in  the  plate.  The  form  and 
position  of  these  on  the  model  will  be  indicated  by  inspection  of 


PLASTER    MODELS.  1 65 

the  form  of  "lateral  cavity"  plates  as  exhibited  in  the  chapter 
on  "  Entire  Dentures." 

There  are  other  modifications  in  the  form  of  cavity  plates, 
some  of  which  are  obsolete;  that  known  as  "  Cleveland's  cham- 
ber" is  still  in  limited  use,  but  does  not  require  a  model  differing 
in  form  from  the  one  described  in  connection  with  full  dentures 
with  central  chambers. 

Manner  of  Obtaining  a  Plaster  Model  from  an  Impression 
in  Plaster,  for  Partial  Dentures. — The  surface  of  the  impres- 
sion in  plaster  should  be  first  glazed,  by  applying  to  it,  with  a 
camel's-hair  brush,  a  uniform  coating  of  varnish,  to  prevent 
adhesion  of  the  model.  Two  kinds  of  varnish  are  in  common 
use — a  transparent  and  colored.  The  former  is  preferred,  for 
the  reason  that  it  penetrates  the  plaster  more  thoroughly,  giving 
to  it  a  greater  depth  of  surface  hardness,  while  the  latter,  if  not 
sufficiently  fluid,  forms  a  somewhat  superficial  incrustation, 
which  is  liable  to  peel  off  in  handling,  leaving  portions  of  the 
model  unprotected.  Either,  however,  if  properly  prepared  and 
applied,  may  be  em.ployed. 

Formtda  N'o.  i.  Formula  No.  2. 

TRANSPARENT  VARNISH.  COLORED  VARNISH. 

Gum  sandarach,  ...     5  oz.  Gum  shellac, ,     5  oz. 

Alcohol, I  quart.       Alcohol, i  quart. 

The  sandarach  and  shellac  should  first  be  freed  from  all  im- 
purities by  careful  picking  and  washing  ;  they  are  then  added  to 
the  alcohol  and  digested  over  a  moderate  heat  until  thoroughly 
dissolved.  Other  substances,  as  gum  elemi,  Venice  turpentine, 
etc.,  have  been  recommended  as  additional  ingredients,  but  they 
are  not  indispensable,  and  may  be  omitted  without  sensibly 
impairing  the  properties  of  the  varnish. 

The  varnish,  or  separating  fluid,  should  be  kept  securely 
bottled,  to  prevent  evaporation  of  the  alcohol,  and  keep  it 
free  from  dust  and  other  foreign  substances.  For  this  purpose 
the  "Clover-Leaf  Holder  (see  Fig.  71)  is  probably  the  most 
convenient,  neat,  cleanly  and  economical  receptacle  on  sale  for 
that  purpose.  The  body  is  of  glass  with  nickeled  mountings 
and  cover.     It   contains  two   compartments,  the  larger    for    the 


IDO  MECHANICAL    DENTISTRY. 

varnish,  the  smaller  for  the  brushes,  of  which  there  are  three, 
a.,  large  one  attached  to  the  lid,  and  two  smaller  ones  which 
depend  from  the  partition  between  the  compartments  by  means 
of  a  little  hook.  Across  the  main  compartment  is  a  scraper  to 
remove  surplus  varnish  from  the  brushes.  The  lid  is  held  in 
place  upon  a  rubber  ring  with  a  firm  pressure,  by  means  of  a 
rubber  wheel  attached  to  a  swinging  lever.  This  makes  the 
holder  air-tight  and  prevents  evaporation  of  the  varnish.  The 
brushes  are  specially  made  for  varnish,  of  fine  goat's  hair,  which 
is  better  for  the  purpose  and  more  durable  than  camel's  hair,  A 
little  alcohol  placed  in  the  brush  compartment  keeps  the  brushes 
pliable  and  is  convenient  for  thinning  the  varnish  when  desir- 
able. 

Fig.  71. 


After  glazing  the  surface  of  the  plaster  impression  with  var- 
nish, a  thin  and  uniform  coat  of  oil  or  soapy  water  should  be 
applied  ;  it  is  then  enveloped,  and  the  model  procured  in  the 
same  manner  as  when  the  other  plastic  materials  are  used. 

The  following  method  of  preparing  the  plaster  impression 
before  it  is  filled  in  for  the  model  is  recommended  by  Dr.  C.  W. 
Spalding :  "  After  the  impression  has  become  hard,  coat  the 
surface  with  a  lather  of  soap  and  water;  wash  this  off  and  im- 
merse the  model  in  water.  This  expels  air  and  avoids  liability 
to  porosity  of  the  surface  of  the  model.  Again  coat  the  surface 
with  a  strong  lather  of  soap  and  water,  and  wash  off  as  before, 
when  the  impression  is  ready  to  receive  the  plaster  for  the 
model.  I  prefer  this  method  to  varnishing,  for  the  reason  that 
the  varnish  used  is  not  always  of  uniform  consistency." 


PLASTER    MODELS.  \6/ 

In  separating  the  model  from  a  plaster  impression,  for  partial 
cases,  it  will  be  necessary  to  cut  the  latter  away  in  pieces,  as  any 
attempt  to  separate  the  two  in  the  ordinary  manner  would 
inevitably  break  away  the  plaster  teeth  from  the  model.  The 
impression  should  be  chipped  away  with  care,  to  avoid  defacing 
the  m.odel.  To  provide  more  perfectly  against  this  accident,  it 
is  better  to  coat  the  impression  with  colored  varnish,  as  this 
will  indicate  with  greater  certainty  the  line  of  contact  or  union 
between  the  two  pieces.  Dr.  Spalding  suggests  a  simple  and 
effective  device  for  the  same  purpose,  which  consists  in  coloring 
the  water  used  to  mix  the  plaster  for  the  impression  with  anilin 
red.  When  separated,  the  model  should  be  trimmed  and  formed 
in  the  manner  before  described. 

Manner  of  Obtaining  a  Plaster  Model  from  an  Impression 
in  Plaster,  for  Entire  Dentures. — The  preparation  of  a  plaster 
impression  of  either  the  upper  or  lower  jaw,  for  full  dentures, 
and  the  method  of  procuring  a  model  therefrom,  differ  in  no 
essential  respect,  except  in  the  mode  of  separation,  from  the 
manipulations  required  when  the  impressions  have  been  taken 
in  plaster  for  partial  pieces.  A  model  can,  ordinarily,  where 
there  are  no  considerable  depressions  or  undercuts  on  the  ex- 
ternal face  of  the  ridge,  be  readily  separated,  either  by  taking 
the  model  in  the  hand  and  tapping  the  handle  of  the  cup,  or  by 
forcing  a  wedge-shaped  instrument  between  the  impression  and 
model  at  the  posterior  border.  When,  however,  there  are  con- 
siderable undercuts,  such  as  usually  prevail  on  either  side  of  the 
median  line  in  front,  above  and  below,  or  the  anterior  and  mid- 
dle portions  of  the  ridge  are  thin,  prominent,  and  overhanging, 
the  application  of  sufficient  force  to  detach  the  impression  in  a 
body  will  inevitably  fracture  such  portions  of  the  ridge  of  the 
model  as  are  engaged  in  the  contracted  spaces.  In  such  cases, 
the  cup  being  removed  from  the  impression,  the  latter  should 
be  grooved  as  deeply  as  possible  without  marring  the  face  of  the 
model,  in  such  a  way  that,  when  the  instrument  is  forced  in  at 
suitable  points,  the  impression  will  be  fractured  on  a  line  with 
the  grooves,  and  thus  be  detached  in  sections.  One  groove  may 
be  made  continuously  along  a  line  corresponding  with  the  sum- 
mit of  the  ridge,  and  others  extending  at  right  angles  with  this 


l68  MECHANICAL    DENTISTRY. 

to  the  outer  borders  of  the  impression.  When  these  external 
sections  are  removed  separately  by  wedging  at  the  extreme  bor- 
der of  the  impression,  the  whole  central  portion  will  be  easily 
detached.  Extreme  thinness  and  prominence  of  the  ridge  will 
most  generally  be  found  in  connection  with  the  lower  jaw,  and 
will  require  cautious  manipulation  to  avoid  accident  to  the 
model.  If  any  portion  of  the  model  should  be  defaced,  it  may 
be  remedied  .by  restoring  the  contour  with  plaster.  After 
detaching  the  model  in  the  manner  mentioned,  the  entire  body 
of  it  should  be  glazed  and  hardened  by  applying  to  it  a  thin 
and  uniform  coat  of  varnish,  if  it  is  to  be  used  in  obtaining  a 
metallic  die.  This  protective  covering  will  prevent  the  surface 
from  wearing,  render  it  more  pleasant  to  the  touch,  facilitate  its 
withdrawal  from  the  sand,  and  give  •  a  more  perfect  mold.  A 
model  may  be  better  prepared  for  permanent  preservation  by 
immersing  it  for  a  short  time  in  a  solution  of  carbonate  of  soda, 
by  which  its  surface  is  converted  into  carbonate  of  lime,  and 
thereby  rendered  hard  and  durable;  care  must  be  taken  not  to 
introduce  any  of  the  bicarbonate  of  soda  into  the  solution. 


CHAPTER   IV. 

METALLIC    DIES   AND    COUNTER-DIES. 

A  Metallic  Die  is  a  fac-siinilc  or  transcript  of  the  mouth  in 
metal,  and  is  also  a  copy  or  likeness  of  the  plaster  model. 

A  Metallic  Counter-die  is  a  copy  of  the  impression,  and  is  a 
reversed  image  of  the  die  and  plaster  model. 

Manner  of  Obtaining  a  Metallic  Die. — Two  general  meth- 
ods are  employed  in  procuring  a  metallic  counterpart  of  the 
model ;  first,  by  vwldiiig ;  secondly,  by  a  process  termed  "  dip- 
pi7tg."  The  first  only,  however, — being  the  more  practical  and 
more  generally  used, — will  be  considered. 

Materials  Used  in  Molding. — For  this  purpose  the  best 
material  is  marble-dust,  though  other  substances,  as  sand,  Spanish 
whiting,  etc.,  have  been  recommended.  Marble-dust  has  the 
advantage  of  being  always  ready  for  use,  as  it  absorbs  sufficient 
moisture  from  the  atmosphere  to  render  it  cohesive,  is  cleanly, 
and  gives  a  smooth  and  uniform  surface  to  the  die.  When  sand 
is  used  it  should  be  fine  and  even-grained,  the  best  for  the  pur- 
pose being  that  used  by  brass  founders.  It  is  prepared  by 
mixing  with  it  sufficient  water  to  render  its  particles  somewhat 
adherent,  so  that  when  portions  of  it  are  pressed  in  the  hand  and 
then  parted  with  the  fingers  it  will  break  away  in  well-defined 
fragments.  Excess  of  water  should  be  avoided,  as  the  vapor 
formed  by  the  molten  metal,  when  poured  upon  it,  will  displace 
portions  of  the  latter  and  form  cavities,  or  blisters,  in  the  face  of 
the  die ;  nor  should  the  sand  used  be  too  dry,  as  in  that  case  it 
will  crumble  away  in  detaching  the  model. 

Oil  has  been  proposed  as  a  substitute  for  water,  in  which  case 
it  is  recommended  to  add  one  quart  of  the  former  to  a  peck  of 
sand.  It  is  claimed  that  the  sand  so  prepared  is  always  in  im- 
mediate readiness  for  use. 

Preparing  Model  Previous  to  Molding. — In  upper  cases, 
whether  partial    or    full,    a    shallow    groove    should    be    made 

169 


I/O  MECHANICAL    DENTISTRY. 

along-  the  posterior  plate  line,  so  that  when  the  plate  is  swaged 
this  edge  will  press  firmly  against  the  roof  of  the  mouth.  The 
cast  should  also  be  carved  at  the  points  where  the  integument 
of  the  palate  is  soft  and  yielding.  In  some  cases  the  center  of 
the  palatal  portion  of  the  mouth  is  unusually  hard  and  unyield- 
ing; in  fact,  large,  bony  prominences  are  sometimes  found;  these 
points  should  have  a  thin  layer  of  wax  placed  over  them,  so  as 
to  relieve  the  pressure,  otherwise  the  plate  would  rock,  thus 
interfering  with  the  adhesion  and  the  wearer's  comfort.  The 
form  for  the  vacuum-chamber  should  also  be  built  up  with  wax 
or  other  material,  when  the  cast  will  be  ready  to  proceed  with 
the  molding. 

Manner  of  Securing  Mold. — The  molding  material  being 
properly  prepared,  the  model  is  placed  with  its  face  uppermost 
on  the  molding  board  and  surrounded  with  a  metallic  ring.  What 
is  known  as  the  Bailey  Molding  Flask  is  used  by  many  opera- 
tors. A  common  "wagon  box,"  however,  of  which  two  or  three 
sizes  should  be  had,  will  answer  every  purpose  in  ordinary  cases. 
If  sand  is  used,  it  should  first  be  well  sifted,  to  remove  the  coarser 
particles,  and  then  filled  into  the  ring,  packing  it  closely  with  the 
fingers  around  and  over  the  model  until  even  with  the  upper  edge 
of  the  box.  Some  care  must  be  observed  in  the  management  of 
the  molding  material  when  packing  it,  for,  if  made  too  compact, 
the  vapor  formed  in  pouring  hot  metal,  failing  to  pass  out  readily, 
will  be  confined  within  the  cavity  and  cause  imperfections  in  the 
face  of  the  die ;  or,  if  too  loosely  packed,  the  fluid  metal,  when 
poured  into  the  mold,  will,  to  some  extent,  permeate  the  pores  of 
the  sand,  or  other  material,  and  render  the  face  of  the  die  rough 
and  imperfect. 

Manner  of  Withdrawing  the  Cast. — After  the  sand  has 
been  well  packed,  level  off  the  surface  with  a  rule,  lift  the  flask 
or  ring  with  its  contents  from  the  bench,  turn  it  over  carefully, 
and  lay  it  down  with  the  bottom  of  the  cast  up.  Now  run  the 
point  of  a  tack  or  the  small  blade  of  a  knife  into  the  center  of 
the  cast  with  a  few  gentle  taps  from  the  hammer.  Grasp  the  knife 
or  head  of  the  tack  firmly  between  the  thumb  and  fingers,  and 
with  a  small  hammer  distribute  a  few  gentle  taps  over  the  sur- 
face of  the  cast.     If  the  cast  cannot  then  be  withdrawn,  continue 


METALLIC    DIES    AND    COUNTER-DIES. 


171 


the  process  and  at  the  same  time  distribute  a  few  gentle  blows 
over  the  edge  of  the  molding  ring,  when  it  will  usually  be  found 
that  the  cast  can  be  readily  lifted  out.  All  these  manipulations 
must  be  very  gentle  or  the  cast  may  be  tilted  or  rocked  in  the 
sand,  and  thus  make  a  false  impression. 

Another  method  of  removing  the  cast  from  the  sand,  usually 
given  in  the  text-books,  is  to  re-invert  the  ring  and  contents, 
hold  it  above  the  table,  and  dislodge  the  cast  by  tapping  it 
gently  underneath.  I  should,  however,  in  nearly  all  cases  reject 
a  mold  from  which  the  cast  had  fallen  out  by  its  own  weight. 

The  Lewis  Molding  Flask. — This  new  form  of  flask,  intro- 
duced by  the  Buffalo  Dental  Manufacturing  Co.,  is  an  improve- 


FiG.  72. 


ment  upon  the  Bailey  Flask  for  molding  dies ;  the  top  part, 
which  forms  the  zinc  die,  being  entirely  new  in  shape  and 
purpose.  By  the  use  of  this  flask,  the  metal  in  the  die  is  con- 
centrated above  it,  so  that  it  has  no  outside  bearing  upon  the 
counter-die ;  thus  overcoming  what  is  to  many  dentists  a  serious 
objection  to  dies  produced  with  the  ordinary  flasks  or  rings, 
viz.,  the  bearing  of  the  die  upon  the  counter,  outside  of  the 
model,  preventing  the  driving  of  the  former  into  the  latter  as  it 
yields  in  swaging,  unless  the  method  suggested  by  Dr.  Broomell 
on  page  178  is  employed.  In  dies  produced  by  the  Lewis  Flask 
the  bearing  of  the  die  upon  the  counter  is  limited  to  the  model, 
and  a  more  perfect  adaptation  can  be  secured  between  it  and 


172  MECHANICAL    DENTISTRY. 

the  plate.  With  this  flask  a  thin  model  can  be  used,  at  the  same 
time  all  the  advantages  of  the  old-fashioned,  thick  or  built-up 
model  secured. 

When  this  form  of  flask  is  employed,  the  procedure  is  as 
follows:  A  thin  plaster  cast  should  be  trimmed  to  give  proper 
draft  at  the  edges,  varnish  and  dry  thoroughly.  Before  pro- 
ceeding to  mold,  dust  it  with  a  little  finely-powdered  charcoal, 
shaking  ofif  all  that  does  not  adhere.  Invert  the  top  or  winged 
section  of  the  flask,  fill  its  conical  cavity  with  sand,  leaving  it  a 
little  high,  and  press  the  back  of  the  model  firmly  upon  it,  to 
secure  a  solid  foundation  and  prevent  rocking.  Place  the  ring  in 
position,  and  sift  the  sand  into  it,  ramming  it  down  carefully. 
Strike  off  the  surface  of  the  sand  level  with  the  top  of  the  ring. 
Reverse  the  flask,  holding  the  sections  together  securely,  then 
remove  the  winged  section  and  draw  the  model.  Fill  the 
depression  in  the  sand  with  the  molten  metal,  then  place  the 
upper  section  of  the  flask  in  position — the  sand  having  pre- 
viously been  knocked  out  of  it — and  complete  the  pouring  of 
the  metal.  When  the  die  has  cooled,  smoke  its  exposed  surface, 
and  replace  it  in  the  winged  part  of  the  flask;  knock  the  sand 
out  of  the  ring,  place  it  in  position,  and  fill  with  the  counter-die 
metal. 

The  Hawes  Flask. — It  not  infrequently  happens  that  the 
ridge  on  the  plaster  model  of  the  upper  jaw  overhangs,  forming 
corresponding  depressions  above,  the  excavations  occurring 
more  commonly  in  front  and  on  each  side  of  the  mesial  line. 
Whenever  this  form  of  the  model  exists,  it  will  be  impracticable 
to  obtain  a  correct  mold  with  either  of  the  methods  j  ust  described, 
since  the  sand,  becoming  impacted  in  these  excavations,  will  be 
broken  away  and  remain  with  the  model  when  the  latter  is  dis- 
lodged. 

The  difficulty  mentioned,  however,  may  be  readily  overcome 
in  all  cases  by  employing  the  sectional  molding  flask  invented 
by  Dr.  G.  W.  Hawes,  the  several  parts  of  which  are  represented 
in  the  accompanying  cuts. 

Fig.  yi^  represents  the  lower  ring,  composed  of  three  movable 
pieces,  with  flange  extensions  that  project  in  toward  the  center. 
When  used,  this  portion  of  the  flask  is  closed  and  the  sections 


METALLIC    DIES    AND    COUNTER-DIES. 


173 


kept  in  place  by  pins  passing  through  the  joints.  Inside  of  this 
ring  the  model  is  placed  face  upward,  the  ridge  extending  a  little 
above  the  upper  plane  of  the  ring.  Sand,  well  sifted,  is  then 
packed  in  around  the  model  on  a  level  with  the  most  projecting 
points  on  the  outside  of  the  ridge,  as  indicated  by  the  dotted 
line  in  Fig.  75.  The  surface  of  the  sand  should  be  trimmed 
smoothly,  and  should  be  cut  squarely  and  at  right  angles  with 
the  ridge  to  prevent  the  sand  from  breaking  away  when  the 
model  is  withdrawn.  Very  finely  pulverized  charcoal,  contained 
in  a  loose  muslin   bag,  is  now  sifted  over  the  exposed  surface  of 


Fig.  t- 


Fig.  74. 


Fig.  75. 


the  sand  to  prevent  the  next  portion  contained  in  the  upper  ring 
from  adhering.  The  plain  ring  (Fig.  74)  is  then  placed  over  the 
one  containing  the  model,  and  is  filled  with  sand  well  packed 
over  the  face  of  the  die.  The  upper  ring  is  now  carefulh-  lifted 
from  the  lower  one  on  a  line  with  the  pins,  thus  separating  the 
two  portions  of  sand,  and  again  exposing  the  uncovered  face  of 
the  model.  One  of  the  pins  should  then  be  drawn  from  the 
lower  ring,  the  sections  of  the  latter  carefully  unfolded,  afid  the 
model  withdrawn  ;  when  the  ring  may  be  again  closed  and  con- 
fined by  replacing  the  pin.  The  upper  ring  is  then  readjusted 
in  its  proper  relation  to  the  lower  one,  the  flask  inverted,  when 


174 


MECHANICAL    DENTISTRY. 


the  mold,  if  the  process  has  been  accurately  conducted,  will  be 
found  perfect. 

In  the  absence  of  the  "  Hawes  "  flask,  the  same  results  may  be 
attained  by  employing  the  following  simple  method,  recom- 
mended by  Dr.  Berhard,  and  subsequently  described  as  follows  : 
"  The  plaster  model  being  prepared  in  the  usual  manner  for 
molding,  varnish  the  front  (or  the  whole)  with  a  thin  solution  of 
shellac.  When  dry,  apply  a  mixture  of  plaster  of  proper  con- 
sistency to  the  front  of  the  model,  from  the  bottom  up  to  the 
edge  of  the  alveolar  line,  spreading  it  on  both  sides  so  as  to 
entirely  fill  up  the  depression  around,  making  the  lower  half 
an  inch  thick,  and  sloping  off  toward  the  alveolar  ridge.  When 
this  has  hardened,  separate  it  from  the  model,  and  draw  the  top 
of  it  over  sand-paper  to  obtain  a  flat  edge,  and  let  it  dry.  Re- 
adjust this  front  piece  to  the  model ;  procure  a  mold  in  sand  or 
other  material,  in  the  usual  way;  place  the  extra  piece  back  in 
its  proper  position  in  the  mold,  and  proceed  to  cast  for  the  die." 

In  obtaining  a  mold  from  the  model  of  a  lower  jaw,  but  little 
difficulty  will  ordinarily  be  experienced  in  obtaining  it  perfect  in 
the  manner  first  described.  The  depressions  at  the  posterior 
and  inner  border  of  the  ridge  are  the  points  most  liable  to  drag 
or  displace  the  sand,  and  when  the  latter  occurs,  the  surplus 
metal  in  the  die  at  such  points  must  be  cut  away  with  suitable 
instruments  ;  or  the  cavities  in  the  model  may  be  so  filled  out 
with  wax  before  molding  as  to  permit  the  ready  separation  of 
the  model  without  displacing  the  sand,  in  which  case,  also,  it 
will  be  necessary,  afterward,  to  trim  the  redundant  metal  from 
the  die. 

Preparing  Cast  for  Mold,  for  Partial  Dentures. — A  die 
is  more  readily  and  accurately  obtained  from  a  model  for  partial 
dentures  by  cutting  away  the  plaster  teeth,  as  before  described. 
The  displacement  of  sand  where  the  ridge  overhangs  will,  as  a 
general  thing,  be  unimportant  in  these  cases,  as  the  base  seldom 
more  than  partially  overlaps  the  border. 

When  whiting  or  marble-dust  is  used  in  molding,  it  is  unneces- 
sary to  mix  water  with  them,  as  the  moisture  which  they 
absorb  from  the  atmosphere  will  give  to  them  the  proper  con- 
sistency. 


METALLIC    DIES    AND    COUNTER-DIES.  1/5 

Preparing  and  Pouring  Metal  for  Dies. — Having  obtained 
a  mold  in  either  of  the  ways  mentioned,  the  metal  designed  for 
the  die  should  be  melted  and  poured  carefully  in  upon  the  more 
prominent  portions  on  the  face  of  the  former.  If  the  metal  is 
raised  much  above  its  fusing  point,  or  the  sand  is  quite  damp, 
the  former  should  be  poured  very  slowly  into  the  mold.  It  is 
better,  however,  that  the  sand  should  be  partially  dried  before 
pouring  the  metal,  and  the  die  cast,  on  the  instant  of  the  metal 
becoming  sufficiently  fluid.  An  observance  of  these  precau- 
tions will  protect  the  sand  from  the  over-action  of  heat,  prevent 
ebullition  of  the  fused  metal  from  the  too  rapid  decomposition 
of  the  water  in  the  sand,  will  give  a  smoother  face  to  the  die, 
and  secure  the  metal  or  metals  from  undue  waste  by  oxidation. 
The  opinion  is  entertained  by  some,  that  greater  shrinkage  of 
the  die  occurs  when  the  metallic  substance  of  which  it  is  com- 
posed is  poured  at  a  temperature  much  above  its  fusing  point ; 
the  fallacy  of  this  is  made  obvious  by  a  moment's  reflection,  as 
a  simple  example  will  show  that  any  change  affecting  the  face  of 
the  die,  as  a  consequence  of  contraction,  can  only  occur  in  the 
metal  between  its  point  of  solidification  or  liquefaction — for  they 
are  identical — and  its  working  temperature.  Zinc,  for  example, 
melts  at  773°.  Now  if  its  temperature  be  raised  to  1200°,  it  will 
remain  fluid  until  it  reaches  773°,  and  in  passing  through  the 
intermediate  degrees  of  heat,  it  will,  in  obedience  to  gravity, 
adapt  itself  perfectly  to  all  parts  of  the  more  depending  portions 
of  the  mold  ;  and  this  perfect  continuity  of  the  two  surfaces 
will  remain  unaffected  by  the  contraction  of  the  metal  until  the 
latter  commences  to  "  set,"  or  solidify,  after  which,  and  not 
until  then,  the  zinc  begins  to  part  from  the  face  of  the  mold  by 
contracting  upon  itself  between  773°  and  the  mean  temperature 
of  the  air.  So  far  as  any  change,  by  contraction,  in  the  face 
of  the  die  is  concerned,  therefore,  it  is  obviously  immaterial 
whether  the  zinc  be  poured  on  the  instant  of  melting  or  at 
1200°  ;  the  result  will  be  the  same  in  either  case. 

The  author  is  indebted  to  Dr.  B.  W.  Franklin  for  the  following 
method  of  securing  metallic  dies  and  counters  by  a  process 
which  greatly  facilitates  the  operation  and  insures  accurate  and 
satisfactory  results  :  "  I  take  all  impressions,  full  and  partial,-  in 


1/6  MECHANICAL    DENTISTRY. 

plaster.  A  small  hole,  less  than  ^^of  an  inch,  is  drilled  through 
the  highest  point  of  the  palatal  surface  of  the  impression, 
through  cup  and  all ;  into  this  place  two  or  three  broom  splints, 
cutting  them  off  even  with  the  surface  of  the  plaster,  to  allow 
any  vapors  to  pass  off  I  sometimes  smoke  the  surface  of  the 
impression.  Around  the  impression  place  sufficient  putty  to 
form  a  ring  the  size  and  height  required  for  the  die.  Into  this 
pour,  at  as  low  heat  as  is  consistent  with  the  mobility  required 
for  sharp  castings,  the  bismuth  alloy  known  as  Sir  Isaac  Newton 
metal,  or,  which  is  better  in  some  respects,  8  parts  bismuth  and 
4  parts  each  of  tin  and  lead — the  latter  composition  being  a 
little  harder.  If  a  little  judgment  is  exercised  in  pouring  either 
of  the  above  alloys,  a  perfect  die  will  be  secured  from  moist 
plaster  impressions  without  any  drying.  As  the  bismuth  is  ex- 
pansive and  the  alloy  is  hard  and  somewhat  brittle,  I  run  only  a 
thin  casting,  not  more  than  half  an  inch  in  thickness,  over  the 
highest  portion  of  the  impression.  I  have  cast-iron  or  brass 
heads  made,  t,}{  inches  in  length,  3  inches  in  diameter  at  the 
large  end,  and  2  inches  at  the  other ;  the  large  end  is  flat,  and 
well  coated  with  common  tinman's  solder.  This  head  is  heated 
until  the  solder  begins  to  soften  ;  it  is  then  placed  in  a  pan  or  other 
convenient  vessel,  and  the  die,  face  side  up,  is  placed  upon  the 
tinned  surface.  When  the  die  begins  to  melt,  and  perfect  union 
is  secured,  cold  water  is  dashed  upon  the  die  and  head  ;  and 
thus  we  have  a  sharp  die,  with  an  iron  head,  to  sustain  the  force 
of  the  blow  in  stamping  the  plate,  and  by  this  means  preventing 
any  spreading  of  the  face  of  the  die  or  liability  of  breaking  in  the 
process  of  swaging. 

"  I  now  take  sheet  lead  of  the  thickness  of  about  No.  24, 
standard  gauge,  and  adapt  it  to  the  face  of  the  die  by  means  of 
a  wooden  mallet  or  burnisher,  or  other  convenient  means.  Trim 
the  lead  plate  to  the  size  required  for  the  plate  to  be  stamped  ; 
when  the  lead  plate  is  nicely  fitted,  remove  it  carefully  from  the 
die  and  place  it  in  a  ring  or  narrow  molding  flask,  the  palatal 
side  up;  now  gently  stamp  molding  sand  into  the  plate  and 
flask,  up  level  with  the  edges  of  the  flask;  then  reverse  the  flask 
and  cut  the  sand  away  c/ean  for  half  an  inch  or  more  down  to 
the.  edge  of  the  lead  plate  all  around.     Around  the   plate  place 


METALLIC    DIES    AND    COUNTER-DIES.  1 7/ 

a  common  molding  ring  sufficiently  large  to  form  the  counter, 
which  is  made  by  pouring  melted  tin  or  lead  (or  any  alloys  of 
these  metals)  on  to  the  lead  plate,  being  careful  not  to  run  the 
metal  so  hot  as  to  melt  the  lead  plate.  When  the  counter  is 
cool  enough  to  handle,  the  adhering  sand  is  brushed  or  washed 
away  ;  the  die  is  then  placed  into  the  bed  or  counter,  and,  with  a 
moderate-sized  hammer,  give  one  or  two  sharp  blows  to  bring  the 
die  and  counter  together.  In  swaging  gold  plates,  two,  three 
or  more  dies  may  be  required  ;  these  may  be  made  either  by  run- 
ning the  die  metal  into  the  impression  (if  not  broken)  or  by 
running  into  lead  plates,  gotten  up  as  before  described,  reserv- 
ing, of  course,  the  first  die  and  counter  for  the  final  swasrinpf  of 
the  plate.  I  ha\e  gotten  up  a  die  and  counter  from  the  impres- 
sion, with  the  aid  of  an  assistant,  in  the  foregoing  manner,  in 
twelve  minutes.  I  usually  get  out  my  die  immediately  after 
taking  the  impression  ;  adapt  a  wax  or  gutta-percha  plate  to  the 
die,  and  get  the  articulation  before  the  patient  leaves  the  office." 

In  the  act  of  contracting,  the  central  portion  of  the  die,  being 
the  last  to  solidify,  is  gradually  drawn  toward  the  periphery, 
forming,  when  the  contraction  is  completed,  an  excavation  of 
greater  or  less  depth  in  the  center  of  its  base,  a  form  unfavorable 
to  an  equal  distribution  of  the  force  applied  in  swaging,  and 
greatly  increasing  the  danger  of  distorting  the  face  of  the  die  by 
cracking  or  spreading,  especially  when  zinc  is  used.  To  con- 
centrate and  equalize  this  force  is  a  matter  of  the  first  import- 
ance. The  liability  to  such  an  accident  may,  to  some  extent,  be 
avoided  by  placing  on  the  die  a  cone-shaped  cap  of  any  hard 
metal,  as  zinc,  brass,  or  cast  iron.  This,  however,  while  it  pro- 
vides against  one-sided  blows  of  the  hammer,  affords  only  a 
partial  remedy,  since  the  same  danger  of  spreading  the  die 
exists,  in  consequence  of  the  cap  resting  on  the  outer  border  of 
the  base  of  the  die,  with  no  central  bearing  whatever.  To 
equalize  the  force  perfectly,  the  cone-shaped  metal  cap  should 
be  incorporated  with,  and  form  part  of  the  body  of,  the  die  itself. 
This  is  partly,  if  not  wholly,  accomplished  by  Dr.  Franklin's 
expedient. 

Counter-die. — A  counter  to  the  die  is  generally  obtained 
directly  from  the  latter,      i.  The  die  is  placed,  face  upward,  upon 


178  MECHANICAL    DENTISTRY. 

the  molding  board,  and  sand,  prepared  as  in  molding,  built  up 
around  it,  leaving  only  the  ridge  and  palatal  face  exposed.  It  is 
then  encircled  with  a  cast-  or  sheet-iron  ring  two  or  three  inches 
deep,  its  edge  imbedded  in  the  sand  to  prevent  the  escape  of  the 
fluid  metal ;  into  this  the  metal  for  the  counter  is  poured  until 
nearly  or  quite  full. 

The  metal  commonly  employed  for  the  counter  is  lead, 
although  other  substances,  as  tin,  type-metal,  some  of  the  more 
fusible  alloys  hereafter  to  be  mentioned,  etc.,  are  sometimes 
employed.  When  the  counter  is  taken  by  pouring  the  metal 
or  metals  composing  it  upon  a  die  fusing  at  a  low  heat,  some 
caution  should  be  observed  lest  the  two  pieces  adhere  by  partial 
fusion  of  the  die.  In  such  cases  the  surface  of  the  die  should  be 
well  protected  with  lamp-smoke  or  whiting,  the  lead  should  be 
poured  at  the  lowest  practicable  temperature,  and  the  conduction 
of  heat  facilitated  by  surrounding  the  die  with  a  heavy  cast-iron 
box  or  ring. 

During  the  process  of  forcing  a  plate  into  adaptation  to  the 
form  of  the  mouth  with  swages,  it  not  infrequently  happens  that 
the  marginal  portions  of  the  former  become  wedged  or  immova- 
bly fixed  between  the  outer  border  of  the  die  and  corresponding 
portions  of  the  counter  before  its  central  portion  is  forced  into 
contact  with  the  palatal  surface  of  the  former,  thus  rendering  it 
difficult  to  conform  the  plate  accurately  to  the  parts  without  the 
application  of  sufficient  force  to  deface  or  otherwise  mar  the 
form  of  the  die.  In  such  cases  the  central  portion  of  the  plate 
may  be  first  swaged  with  a  partial  counter,  which  is  made  to 
receive  only  the  palatal  portion  and  upper  surface  of  the  ridge 
of  the  die.  This  method,  as  practised  and  described  by  Dr.  I. 
N.  Broomell,  of  the  Pennsylvania  College  of  Dental  Surgery,  is 
as  follows  : — 

Progressive  Counter-dies. — "  It  being  desirous,  in  swaging  a 
plate,  to  have  the  palatine  portion  forced  into  position  at  the 
beginning,  the  first  counter-die  should  be  formed  as  represented 
in  Fig.  'jt).  To  accomplish  this  the  sand  must  be  built  entirely 
over  the  ridge,  allowing  only  the  palatine  portion  of  the  die  to 
be  exposed.  The  second  counter-die  should  extend  just  beyond 
the  center  of  the  ridge,  as  shown  in   Fig.  jy ,  and  the  tliird  or 


METALLIC    DIES    AND    COUNTER-DIES. 


179 


final  counter  may  be  formed  in  the  usual  manner,  see  Fig.  78. 
By  the  judicious  construction  of  this  series  of  counter-dies,  more 
satisfactory  results  are  obtained,  and  much  needless  use  of  the 
horn  mallet  dispensed  with.  It  will  readily  be  observed  that  a 
counter-die  formed  as  represented  in  Fig.  76  will  drive  the  center 


Fig.  76. 


Fig.  77. 


Fig.  78. 


of  the  plate  into  position  without  the  usual  resistance  experi- 
enced in  using  the  ordinary  counter.  The  use  of  No.  ii  (Fig. 
'J'])  will  gradually  start  the  plate  over  the  ridge,  and  No.  iii  will 
readily  complete  the  process." 

As  before  remarked,  preference  is  usually  given  to  lead  in  the 
formation  of  a  counter-die,  mainly  on  account  of  its  greater  soft- 
ness.    This  property  in  a  counter  is  practically  important.     In 


l80  MECHANICAL    DENTISTRY. 

the  process  of  forcing  a  metallic  plate  into  adaptation  to  the 
mouth,  partial  displacement  or  yielding  of  either  the  die  or 
counter,  or  of  both,  necessarily  occurs,  and  it  is  scarcely  neces- 
sary to  remark  that  whatever  change  of  form  is  produced  should 
take  place  wholly  in  the  counter,  otherwise  deformity  of  the  die 
must  ensue. 

Essential  Properties  of  a  Die. — There  are  certain  proper- 
ties which  it  is  indispensable  that  a  metallic  die  should  possess 
in  order  to  answer  fully  the  requirements  of  the  dentist. 

1.  A  die  should  be  sufficiently  liard  to  resist  any  necessary 
force  applied  to  it  in  stamping  the  plate  without  suffering  any 
material  change  in  the  form  of  its  face,  by  which  latter  term  is 
meant  that  portion  of  the  die  with  which  the  plate  is  brought 
in  contact.  This  property  is  most  indispensable  in  those  cases 
where  the  arch  of  the  mouth  is  very  deep,  the  rugae  prominent 
and  sharply  defined,  and  whqre  the  alveolar  ridge  is  marked  by 
angular  and  abrupt  prominences  and  depressions.  In  such 
cases,  if  the  die  is  not  sufficiently  resistant,  the  points  most 
prominent  upon  its  face  will  be  bruised  or  battered  down,  while 
the  plate  will  fail  to  be  forced  perfectly  into  the  cavities  or  depres- 
sions, and  its  coaptation  to  the  mouth,  to  that  extent,  rendered 
faulty.  The  case  in  which  a  less  degree  of  hardness  is  admis- 
sible is  where  the  arch  of  the  mouth  is  broad  and  shallow,  the 
rugae  imperfectly  defined,  and  the  ridge  regular  and  symmetrical. 
The  conformation  of  the  mouth,  therefore,  will,  in  respect  to  the 
property  of  hardness,  admit  of  some  latitude  in  the  choice  of 
the  metal  or  alloy  employed  in  the  formation  of  a  die. 

2.  Another  important  property  of  a  metallic  die  is  non-con- 
traction, so  far,  at  least,  as  this  is  attainable.  Inasmuch  as  the 
successful  adaptation  of  the  plate  depends,  in  a  great  measure, 
upon  an  accurate  representation  of  the  precise  form  of  the  mouth 
in  the  die,  it  is  of  the  first  importance  that  the  latter,  other 
requisites  being  secured,  should  be  composed  of  some  metal  or 
metals  having  the  least  possible  contraction  in  cooling.  Con- 
traction is,  in  varying  degrees,  common  to  all  metals  exposed  to 
a  decreasing  temperature,  and  it  is  impossible,  therefore,  to  obtain 
a  perfectly  faultless  copy  of  the  mouth  in  metal.  Fortunately, 
as  well  for  the  expert  as  the  unskilled  manipulator,  the  unavoid- 


METALLIC    DIES    AND    COUNTER-DIES.  lOl 

able  shrinkage  incurred  is  partially  or  wholly  compensated  for, 
by  the  expansion  of  the  plaster  model  and  the  yielding  condi- 
tion of  the  soft  tissues  of  the  mouth,  but  under  no  circum- 
stances should  the  accommodation  afforded  by  the  condition  last 
mentioned  encourage  negligence  or  unskilfulness  in  the  use  of 
all  available  means  necessary  to  secure  the  most  accurate  adap- 
tation of  the  base.  Ordinarily,  a  moderate  degree  of  contraction 
will  not  materially  impair  the  fit  of  a  plate ;  on  the  contrary,  in  the 
case  of  the  upper  jaw,  it  sometimes  favors  its  adhesion  and  reten- 
tion in  the  mouth.  Cases,  on  the  other  hand,  frequently  occur 
where  the  least  practicable  amount  of  shrinkage,  even  at  the  par- 
tial sacrifice  of  other  properties,  becomes  indispensable  in  the  die. 
3.  A  third  important  requisite  of  a  die  is  f visibility.  Aside 
from  the  convenience  incident  to  the  use  of  metals  which  fuse  at 
a  low  heat,  there  is  another  consideration  favoring  this  property 
of  more  practical  importance.  It  is  well  known  that  all  metals 
expand  by  heat  and  contract  by  cold.  In  obedience  to  this  law, 
metals  fusing  at  a  high  heat  suffer  a  greater  aggregate  contrac- 
tion than  those  melting  at  a  lower  temperature,  and,  as  between 
two  metallic  bodies  of  equal  dimensions,  liquefying  at  different 
temperafures,  the  difference  in  contraction  will  correspond 
exactly  with  the  difference  in  the  number  of  degrees  through 
which  each  passes  from  the  point  of  solidification  to  the  mean 
temperature  of  the  air,  allowance  being  made  for  the  difference 
in  their  ratios  of  contraction.  Two  dies,  one  composed  of  copper 
and  the  other  of  zinc,  will  serve  to  illustrate.  Fused  copper 
solidifies  at  1900°.  In  cooling,  therefore,  it  contracts  through 
over  1800°  to  reach  a  working  temperature,  while  zinc,  fusing  at 
773°,  contracts  through  only  about  700°  to  reach  the  same  tem- 
perature. As  before  stated,  the  difference  in  the  contraction  of 
metals  will  be  somewhat  modified  by  that  in  their  ratio  of  contrac- 
tion, but  it  will  always  be  found  that  the  more  fusible  metals  have 
the  least  aggregate  shrinkage  whenever  any  considerable  dis- 
parity exists  between  their  fusing  points.  It  is  in  accordance 
with  the  principles  here  set  forth  that  the  more  fusible  alloys, 
some  of  which  melt  at  remarkably  low  temperatures,  are  employed 
whenever  it  is  important  to  obtain  a  die  as  nearly  the  exact 
counterpart  of  the  model  as  possible. 


1 82  MECHANICAL    DENTISTRY. 

4.  Finally,  a  die  should  be  sufficiently  cohesive  to  resist  the 
repeated  blows  of  a  heavy  hammer  without  parting  or  cracking- 
Many  metals,  as  antimony,  bismuth,  etc.,  in  other  respects  suit- 
able for  dies,  are  objectionable  on  account  of  brittleness.  But  it 
must  not,  therefore,  be  inferred  that  all  metals  that  are  denomi- 
nated brittle  are  inadmissible  for  this  purpose  ;  for  zinc,  which  in 
its  ordinary  condition  is  ranked  as  a  brittle  metal,  and  type- 
metal,  which  is  always  so,  are  in  no  danger  of  being  forced  asunder 
or  of  suffering  displacement  when  in  the  compact  form  of  a  die, 
provided  the  force  used  in  swaging  is  judiciously  applied,  or 
proper  form  and  sufficient  depth  are  given  to  the  body  of  the 
die. 

To  recapitulate  briefly  :  a  die  should  be  formed  of  some  metal 
or  alloy  that  has  a  surface  hardness  sufficient  to  resist  compres- 
sion ;  that  fuses  at  a  low  temperature ;  that  does  not,  in  any 
material  degree,  contract  in  the  act  of  cooling;  and  whose  par- 
ticles adhere  with  sufficient  cohesive  force  to  maintain  perfectly 
its  integrity  of  form  under  the  hammer.  Any  one  or  two  of 
these  properties  are  readily  attainable  in  the  same  die,  but  no  one 
known  metal  or  alloy  combines  all  of  them  perfectly.  Thus 
either  cast-iron,  brass,  bronze,  or  cannon  metal  would  "form  an 
excellent  material  in  respect  of  surface  hardness,  and  in  the  com- 
pact form  of  a  die  would  be  sufficiently  cohesive,  but  few  enjoy 
convenient  facilities  for  melting  them  ;  besides,  their  great  con- 
traction consequent  upon  their  high  fusing  point  would  render 
their  employment  entirely  inadmissible.  Again,  certain  alloys,  as 
those  composed  of  lead,  tin,  and  antimony  or  bismuth,  are  emi- 
nently suitable  on  account  of  their  ready  fusibility  and  compara- 
tive exemption  from  shrinkage,  but  they  gain  these  properties  at 
the  expense  of  that  degree  of  hardness  necessary  to  resist  com- 
pression. Tin  in  its  uncombined  state  is  ordinarily  sufficiently 
fusible,  tenacious,  and  non-contractile,  but  is  too  soft  and  yield- 
ing when  forcibly  compressed.  Antimony  and  bismuth  are  suffi- 
ciently hard,  fusible,  and  non-contractile,  but  are  objectionable 
on  the  score  of  extreme  brittleness. 

Any  metallic  substance  that  combines  most  perfectly  the 
several  properties  referred  to  is,  therefore,  best  adapted  to  the 
necessities  of  the  mechanical  operator,  and  experience  has  almost 


METALLIC    DIES    AND    COUNTER- DIES.  1 83 

universally  accorded  pre-eminence  in  this  respect  to  zinc.  It 
presents  a  more  resistant  surface  to  the  blow  of  a  hammer  than 
either  copper  or  brass,  three  times  more  so  than  that  of  tin,  and 
more  than  double  that  of  type-metal.  As  it  usually  occurs  in 
commerce  it  may  be  classed  as  a  brittle  metal,  but  when  annealed 
it  is  tough  and  malleable.  It  melts  at  a  heat  (773°)  which  may 
be  readily  commanded,  and  contracts  but  little  in  cooling.  The 
late  Professor  Austen  demonstrated  by  actual  experiments  that 
an  av^erage-sized  zinc  die  measuring  two  inches  transversely  con- 
tracts yl-iro-  of  an  inch  from  outside  to  outside  of  the  alveolar 
ridge,  being  equivalent  in  thickness  to  three  ordinary  leaves  of  a 
journal.  Professor  Austen  remarks  :  "  In  the  first  case  (upper 
jaw)  the  plate  would  '  bind,'  and  if  the  ridge  were  covered  by  an 
unyielding  mucous  membrane  it  would  prevent  accuracy  of 
adaptation.  In  the  second  case  (under  jaw)  the  plate  would 
have  too  much  lateral  '  play,'  and  consequently  lack  stability. 
Again,  in  a  moderately  deep  arch,  say  half  an  inch  in  depth,  the 
shrinkage  between  the  level  of  the  ridge  and  the  floor  of  the 
palate  will  be  nearly  ytjVu — I'ather  more  than  one  leaf  of  a 
journal.  In  the  deepest  arches  this  shrinkage  becomes  a  serious 
difficulty ;  in  the  shaljower  cases  it  is  not  of  much  moment,  as 
there  is  no  mouth  so  hard  as  not  to  yield  the  yttVo  ^''timTo'  ^^  ^^ 
inch." 

As  before  stated,  a  moderate  degree  of  shrinkage  in  the  die 
may,  in  certain  conditions  of  the  mouth,  practically  favor  the 
adhesion  and  permanent  retention  of  a  plate  applied  to  the  upper 
jaw.  The  conditions  alluded  to,  and  which  prevail  in  a  greater 
or  less  degree  in  all  cases,  are,  soft  and  yielding  ridge  and  com- 
paratively hard  and  unimpressible  palate.  Now,  if  in  the  first 
instance  the  plate  is  swaged  into  uniform  contact  with  all  parts 
of  the  jaw,  it  will  be  readily  perceived  that  if  pressure  is  made 
over  the  ridge  on  one  side  the  latter  will  yield,  while  the  central 
portion  of  the  plate,  meeting  with  a  fixed  point  of  resistance  at 
the  floor  of  the  palate,  will  "ride"  upon  the  latter,  and  thus 
throw  the  plate  from  the  ridge  on  the  opposite  side  of  the  jaw. 
If,  however,  a  space  equal  to  one  or  two  thicknesses  of  the  plate 
exists  between  the  latter  and  the  roof  of  the  mouth,  as  a  conse- 
quence of  contraction  in  the  die,  the  plate,  as  it  is  carried  against 


184  MECHANICAL    DENTISTRY. 

the  palate,  in  the  act  of  exhausting  the  air  from  beneath  it,  will  at 
the  same  time  forcibly  compress  the  ridge,  securing  thereby  a 
more  resistant  basis  along  the  border,  and  providing  more  cer- 
tainly against  displacement  of  the  base  on  the  application  of 
forces  brought  to  bear  upon  it  in  mastication. 

The  extent  to  which  the  shrinkage  of  a  die  may  be  admitted 
in  any  given  case  will  depend  partly  upon  difference  in  the 
conditions  heretofore  mentioned  in  the  soft  parts  of  the  mouth,  and 
in  part,  also,  upon  the  general  configuration  of  the  jaw.  In  a 
medium-sized  mouth,  with  a  depth  of  say  half  an  inch  to  the 
arch,  a  moderately  soft  ridge  and  resisting  palate,  the  shrinkage 
incident  to  zinc  will  be  unimportant,  and  in  many  cases  will  be 
advantageous.  If,  however,  the  vault  is  very  deep,  even  though 
there  be  a  yielding  ridge,  the  unavoidable  contraction  of  a  zinc 
die  will  throw  the  plate  so  far  from  the  arch  as  to  render  it  dif- 
ficult for  the  patient  to  exhaust  the  atmosphere  from  between  it 
and  the  floor  of  the  palate,  and  even  when  the  latter  is  practi- 
cable, the  plate  will  bind  with  such  force  upon  the  outer  border 
of  the  ridge  as  not  only  to  produce  pain  and  irritation  of  the 
compressed  parts,  but  the  resistance  afforded  at  these  points  will 
be  sufficient,  in  many  cases,  to  break  up  the  adhesion,  and  force 
the  plate  from  the  palate.  Again,  as  an  extreme  case,  if  the 
ridge  and  palate  are  somewhat  uniformly  unyielding,  and  the  pal- 
atal vault  is  at  the  same  time  very  deep,  a  zinc  die  can  only  be 
made  available  in  bringing  the  base  as  nearly  into  adaptation  as 
possible,  after  which  the  operation  may  be  completed  with  a 
swage  having  a  less  degree  of  shrinkage,  and  which,  as  a  mere 
finishing  die,  need  not  necessarily  be  so  hard  as  zinc. 

In  conforming  a  plate  to  the  lower  jaw,  the  die  should  be  as 
free  as  possible  from  contraction  in  all  cases.  The  greatest 
shrinkage  in  such  cases  will  be  between  the  posterior  extremities 
of  the  ridge,  giving  too  much  lateral  play  to  the  plate ;  in  ad- 
dition to  which  the  posterior  and  inner  edge  of  the  base,  pro- 
jecting out  from  the  ridge,  will  obstruct  the  free  action  of  the 
tongue,  while  the  latter  will  tend  to  lift  it  from  the  ridge  and 
render  it  unstable.  These  conditions  may  be  partially  remedied 
by  turning  the  edge  of  the  plate  in  against  the  ridge  with  pliers  ; 
but    this  expedient    should    never   be    resorted    to    in  any  case 


METALLIC    DIES    AND    COUNTER-DIES.  1 85 

whenever  it  is  practicable  to  secure  a  correct  adaptation  by- 
swaging. 

In  all  cases  in  which  a  zinc  die  fails  to  bring  the  plate  into 
proper  adaptation  to  the  parts,  either  of  the  following  metallic 
compounds  may  be  used  to  complete  the  process  after  partial 
stamping  with  zinc. 

Type  Metal. — Lead,  five  parts  ;  antimony,  one  part.  Fuses 
at  500°  ;  contraction  less  than  one-half  that  of  zinc  ;  more  com- 
pressible than  the  latter  and  very  brittle. 

Babbitt  or  Anti-Friction  Metal. — Copper,  three  parts  ;  anti- 
mony, one  part  ;  tin,  three  parts.  First  fuse  the  copper,  and  then 
add  the  antimony  and  tin.  Melts  at  a  moderately  low  heat ; 
contracts  but  little;  is  brittle,  but  may  be  rendered  less  so  by 
adding  tin. 

Zinc,  four  parts  ;  ////,  one  part.  Fuses  at  a  lower  heat,  contracts 
less  in  cooling,  and  has  a  less  surface  hardness  than  zinc. 

Tm,  five  parts  ;  ajitiinony,  one  part.  Melts  at  a  lower  heat  than 
either  of  the  preceding  alloys  ;  contracts  but  slightly  in  cooling  ; 
is  harder  than  tin  and  sufficiently  cohesive.  It  is  readily  oxid- 
ized and  should   be  poured   as    soon  as  melted. 

Fusible  Alloys. — The  following  tabular  view  of  the  more 
fusible  alloys,  the  respective  properties  of  which  are  deduced 
from  actual  experiments,  was  given  by  Professor  Austen  in  a 
paper  on  "  Metallic  Dies."*  Zinc  is  introduced  into  the  table 
for  the  purpose  of  comparison. 


Melting      Contrac-    u     j  Brittle- 

°      ^-i-.  Hardness, 

point.  tility.  ness. 


1.  Zinc, 770° 

2.  Lead,  2,  Tin,  i, 440° 

3.  Lead,  i,  Tin,  2, 340° 

4.  Lead,  2,  Tin,  3,  Antimony,   i,     ....  420° 

5.  Lead,  5,  Tin,  6,  Antimony,  i,      ....  320° 

6.  Lead,  5,  Tin,  6,  Antimony,  i,  Bismuth,  3,  300° 

7.  Lead,  i.  Tin,  i,  Bismuth,  i 250° 

8.  Lead,  5,  Tin,  3,  Bismuth,  8, 200° 

9.  Lead,  2,  Tin,  i,  Bismuth,  3, 200° 


.01366 

.018 

5 

.00633 

.050 

3 

.00500 

.040 

3 

■00433 

.026 

7 

.00566 

■035 

6 

.00266 

.030 

9 

.00066 

.042 

7 

.00200 

.045 

8 

•00133 

.048 

7 

Professor  A.,  in  commenting  on  the  preceding  table,  observes  : 

*  American  Journal  of  Denial  Science,  vol.  vi,  page  367. 


1 86  MECHANICAL    DENTISTRY. 

"  The  last  column  contains  an  approximate  estimate  of  the  rela- 
tive brittleness  of  the  samples  given.  As  in  the  other  columns, 
the  low  numbers  represent  the  metals,  so  far  as  this  property  is 
concerned,  most  desirable.  Those  marked  below  5  are  malleable 
metals  ;  those  above  5  are  brittle  ;  zinc,  marked  5,  separates  these 
two  classes,  and  belongs  to  one  or  the  other,  according  to  the 
way  in  which  it  is  managed."  Allusion  is  here  made  to  the  pro- 
cess of  annealing  zinc,  which  has  already  been  adverted  to  when 
considering  the  latter  metal  in  the  former  part  of  the  work.  The 
special  method  employed  is  thus  described  by  the  author  already 
quoted  :  "  The  simplest  way  to  anneal  a  zinc  die  is  to  place  it  in 
the  melting  ladle  with  about  a  tablespoonful  of  water,  removing 
it  in  thirty  seconds  after  the  water  has  boiled  away.  If  the  fire 
is  a  very  hot  one,  remove  it  immediately  on  the  disappearance  of 
the  water.  It  will  often  happen  that  the  die  is  annealed  in  the 
process  of  taking  the  counter-die.  This  will  more  certainly 
occur  when  Nos.  7,  8,  or  9  (see  table)  are  used  for  the  counter. 
For  example,  take  tin,  using  a  mass  twice  the  size  of  the  die  ; 
should  it  be  heated  to  540°  (100°  above  melting  point),  it  would 
not,  allowing  for  loss  of  heat  by  radiation  and  contact  with  the 
cast-iron  ring  (if  one  be  used),  heat  the  zinc  beyond  330°.  Lead, 
cast  as  cool  as  it  could  possibly  be  poured,  unless  in  a  very  heavy 
ring  (such  as  a  '  cart-wheel  box  '),  or  in  quantity  too  small  for  a 
well-shaped  counter,  would  be  apt  to  raise  the  zinc  at  least  400°, 
and  so  impair  its  malleability,  whilst,  if  poured  as  hot  as  many 
are  in  the  habit  of  doing,  the  zinc  will  remain  as  brittle  as  when 
first  cast." 


CHAPTER   V. 

PARTIAL   DENTURES. 

The  almost  unlimited  modifications  in  the  form  of  substitutes 
designed  to  supply  the  loss  of  a  portion  only  of  the  natural  teeth 
and  the  difficulties  oftentimes  incident  to  a  harmonious  arrange- 
ment of  the  teeth  of  replacement,  as  well,  also,  as  the  impracti- 
cability of  always  securing  a  perfectly  satisfactory  and  efficient 
antagonism  or  closure  of  the  artificial  with  the  natural  organs, 
frequently  surround  this  process  with  peculiar  embarrassments, 
and  often  render  their  successful  application  extremely  difficult. 
They  will,  accordingly,  be  found  to  demand  of  the  operator  the 
exercise  of  greater  skill,  ingenuity,  and  discrimination  than  are 
usually  required  of  him  in  the  construction  and  application  of 
entire  dentures. 

Certain  general  and  characteristic  forms  of  substitutes  of  the 
kind  under  consideration  derive  their  distinctive  character  from 
the  several  means  employed  in  fixing  or  retaining  them  in  the 
mouth.    These  means  of  retention  may  be  classified  as  follows  : — 

1.  The  roots. of  the  natural  teeth  as  supports  for  single  artifi- 
cial crowns,  and  for  so-called  bridge-work. 

2.  Clasps  attached  to  the  remaining  natural  teeth. 

3.  Atmospheric  pressure  and  adhesion. 

Crown-  and  Bridge-work. 

Introductory  Remarks. — Under  the  first  head  given  above, 
for  supporting  partial  artificial  dentures,  the  various  methods  of 
constructing  and  attaching  single  artificial  crowns,  and  the  allied 
method  of  replacement  known  as  bridge-work,  will  be  considered. 

Though  the  proper  construction  of  a  modern  collar  crown  or 
bridge  denture  requires  much  scientific  information,  unusual 
skill,  and  sound  judgment,  a  great  portion  of  the  work  entailed 
is  necessarily  done  in  the  laboratory.     It  should,  therefore,  have 

187 


150  MECHANICAL    DENTISTRY. 

a  place  in  every  work  embracing  the  subject  of  prosthetic  dentis- 
try. It  demands,  in  fact,  a  distinctive  place,  as  it  is  one  of  the 
most  important  and  exacting  branches  of  dental  practice. 

As  Dr.  George  Evans  has  well  said,  modern  crown-  and  bridge- 
work,  properly  understood  and  properly  performed,  takes  high 
rank  in  dental  art,  and  offers  wide  scope  for  versatility  of  talent 
and  inventive  genius.  The  varied  and  complicated  cases  pre- 
sented for  treatment  frequently  suggest  to  the  expert  novel  con- 
trivances and  methods  of  construction  and  application.  Suc- 
cessful practice  of  crown-  and  bridge-work  depends  upon  a 
thorough  mastery  of  the  underlying  principles,  and  expertness 
in  the  processes  involved,  governed  by  sound  judgment  and 
perfect  candor.  When  practised  by  dentists  possessing  the 
requisite  attainments  and  governed  by  correct  ethical  principles, 
it  gives  results  which  are  gradually  establishing  its  value,  remov- 
ing erroneous  impressions,  and  insuring  a  wide  professional  and 
public  indorsement. 

There  are,  however,  limits  to  the  utilization  of  these  means  of 
support.  There  are  many  roots  wholly  unsuitable  for  the  pur- 
pose. The  operation  may  be  said  to  be  valuable  in  proportion 
as  the  artificially-crowned  root  can  be  made  comfortable,  service- 
able, and  durable.  A  pulpless  root  that  is  extensively  disinte- 
grated, or  that  is  greatly  denuded  from  excessive  absorption  of 
the  surrounding  alveolus,  or  very  loose  in  consequence  of 
extended  destruction  of  the  investing  membranes,  cannot,  in  any 
sufficient  degree,  meet  these  requirements.  Between  these 
extreme  conditions  on  the  one  hand,  and  those  associated  with 
partially  crownless  roots  with  the  pulp  intact,  the  investing 
membranes  free  from  disease,  the  cervical  portions  of  the  bony 
structure  unimpaired  by  decay,  and  a  firm  attachment  to  the 
socket,  conditions  representing,  on  the  other  hand,  an  opposite 
extreme,  there  are  graduations  of  normal  and  abnormal  states, 
which,  while  they  may  not  exclude  the  operation,  must,  in  some 
degree,  impair  its  value.  Any  estimate  of  the  absolute  value  of 
this  method  of  substitution  that  excludes  a  recognition  of  this 
fundamental  truth  is  a  false  and  unwarranted  one,  and  there  can 
be  no  rational  prognostication  in  these  cases  that  does  not  admit 
this  truth  as  an  essential  element  in  forecasting  results. 


ROOT    CROWNING.  I  89 

Not  onl»will  results  be  modified  by  conditions  immediately- 
associated  with  the  root  to  be  operated  on,  but  also,  to  some 
extent,  by  the  general  health  of  the  mouth.  Any  abnormal 
states  of  either  the  hard  or  soft  tissues,  or  the  presence  of  for- 
eign deposits,  will  act  as  predisposing  causes  in  the  development 
of  unfavorable  conditions  whenever  the  root  operated  on  has, 
previous  to  curative  treatment,  been  morbidly  affected,  and 
especially  if  such  diseased  conditions  have  been  somewhat  viru- 
lent and  of  long  standing.  It  is  best,  therefore,  in  all  cases  to 
inspect  the  mouth  carefully  before  attaching  the  crown,  and  if 
any  of  the  remaining  teeth  are  found  carious  or  incrusted  with 
tartar,  or  the  mucous  membrane  and  gums  are  inflamed  or 
otherwise  diseased,  appropriate  treatment  should  be  directed  to 
the  correction  of  such  abnormal  conditions  as  may  be  present. 

In  the  less  favorable  class  of  cases,  or  where  the  root  has 
been  previously  diseased,  though  subsequently  restored  to  a 
healthy  condition,  any  diathesis  or  constitutional  tendency  pre- 
disposing to  inflammation  or  suppuration,  may  become  a  factor 
in  the  development  of  unfavorable  results.  Whenever  this 
predisposition  exists  in  any  marked  degree,  the  operation  should 
be  performed  in  the  most  careful  manner,  avoiding  as  far  as  pos- 
sible all  sources  of  irritation  in  the  use  of  stones,  saws,  drills, 
and  in  tapping  and  malleting,  and  especially  in  the  use  of  excis- 
ing forceps  for  the  removal  of  any  remaining  portions  of  the 
crown.  Should  any  tenderness  or  loosening  of  the  root  super- 
vene after  its  necessary  preparation,  and  before  setting  the 
crown,  it  will  be  prudent  to  defer  the  completion  of  the  opera- 
tion until  there  is  a  subsidence  of  the  morbid  conditions,  for, 
if  by  reason  of  such  irritation  or  inflammation,  suppuration 
should  be  re-established,  it  may  be  necessary  to  free  the  pulp 
canal  and  renew  treatment  through  the  apical  foramen. 

The  success  of  the  operation  may  also  be  greatly  impaired  by 
careless,  hurried,  and  injudicious  manipulation;  as  where  the 
remaining  portions  of  the  natural  crowns  of  the  tooth  are 
violently  removed  with  excising  forceps,  by  the  unskilful  use 
of  instruments  in  dressing  the  root,  by  drills  in  enlarging  the 
central  cavity,  by  undue  or  misapplied  force  in  the  final  adjust- 
ment of  the  artificial  crown,  or,  finally,  by  a  faulty  position   of 


IQO 


MECHANICAL    DENTISTRY. 


Fig   79. 


the  tooth  of  replacement,  by  which  the  root  is  subjected  to 
injurious  strain,  either  by  lateral  pressure  or  premature  closure 
against  those  of  the  opposite  jaw.  By  the  operation  of  either 
or  all  of  these  causes,  disease  of  a  more  or  less  intractable  char- 
acter may  be  induced  which  will  impair  the  usefulness  of  the 
artificial  organ  and  subject  the  patient  to  much  annoyance. 

Preparation  of  the  Root. — In  the  process  of  preparing  the 
root  for  the  attachment  of  an  artificial  tooth,  all  remaining  por- 
tions of  the  natural  crown  should  first  be  removed  with  suitable 
instruments.  If  the  cervical  portion  of  the  tooth  is  compara- 
tively sound  and  unbroken,  this  may  be  most  expeditiously 
accomplished,  and  with  less  risk  of  injury  to  the  root,  by  cut- 
ting two  parallel  grooves,  opposite  each  other,  on  the  labial  and 
palatal  surfaces,  with  a  small  circular  saw,  or  a  hard  rubber  or 
rubber  and  corundum  disk.  These  grooves 
should  be  cut  through  the  enamel  deep  into 
the  dentine.  Then  with  the  excising  forceps, 
the  cutting  edges  of  which  are  placed  in  the 
grooves,  the  crown  is  readily  severed  from  the 
root. 

After  the  use  of  the  disks  and  excising  for- 
ceps, any  remaining  portions  projecting  beyond 
the  free  margins  of  the  gum  should  be  re- 
moved and  proper  shape  given  to  the  end  of 
the  root.  A  flat-edged  corundum  stone  or 
what  are  known  as  the  Ottolengui  root  facers 
(Fig.  79)  are  the  best  for  the  purpose,  and  when 
in  use  the  stones  should  be  kept  constantly  wet  and  free  from 
clogging  particles  of  tooth  substance.  The  end  of  the  root 
should  be  dressed  down,  anteriorly,  a  little  below  the  free 
margin  of  the  gum,  care  being  taken  not  to  cause  unnecessary 
laceration;  in  this  way  the  artificial  crown,  when  adjusted  to  the 
root,  will  unite  so  intimately  with  the  gum  in  front,  in  ordinary 
cases,  as  to  render  exposure  unnecessary.  The  surface  of  the 
root  prepared  in  this  manner  will  present  a  concavity  corre- 
sponding with  the  festoon  of  the  gum. 

If  a  living  pulp  remains  in  the  root,  it  will  not  ordinarily  be 
practicable, — unless  there  is  partial  obliteration  and  consequent 


ROOT    CROWNING.  I9I 

recession  of  the  pulp  cavity  as  the  result  of  ossific  deposits, — 
either  to  cut  off  the  tooth  on  a  line  with  the  gum  or  even  trans- 
versely, or  to  dress  the  root  even  with  the  gum,  without  inflict- 
ing insufferable  pain.  It  will  be  necessary,  therefore,  under 
such  circumstances,  either  to  devitalize,  and  extirpate  the  pulp 
through  the  carious  opening  in  the  crown  before  the  latter  is 
removed,  or  (if  not  exposed  by  excising  the  tooth),  through  an 
opening  into  the  pulp,  made  with  a  drill  revolved  by  the  dental 
engine,  after  excision. 

Devitalization  of  the  Pulp. — There  are  several  ways  of  ex- 
tirpating a  dental  pulp.  One  of  the  older  and  still  not  uncom- 
mon methods  of  operating  consists,  first,  in  devitalizing  it  with 
arsenious  acid  and  then  removing  it  with  a  broach.  Another 
method  practiced  by  some  is  to  thoroughly  expose  the  pulp, 
apply  cocain  and  then  extract  the  pulp  with  a  broach. 

Excision  of  Crown  and  Instantaneous  Extirpation  of  the 
Pulp. — A  somewhat  heroic  method,  though  one  with  which  the 
writer  has  had  much  satisfaction,  by  which  a  living  pulp  may  be 
quickly  and  successfully  removed,  with  comparatively  little 
pain,  consists  in  cutting  the  labial  and  palatal  grooves  as  has 
been  directed,  making  them  as  deep  as  possible,  without  inflict- 
ing too  much  pain ;  then  with  the  excising  forceps,  the  cutting 
edges  of  which  are  inserted  in  these  grooves,  the  crown  is 
quickly  severed  from  the  root.  This  usually  leaves  the  pulp 
fully  exposed  and  paralyzed,  when  a  piece  of  orange  wood — 
previously  cut  and  shaped  to  about  the  size  of  the  canal,  not 
larger,  and  the  point  saturated  with  carbolic  acid — is  carefully 
placed  against  the  exposed  point  of  the  pulp  and  quickly  driven 
with  one  light  blow  from  the  mallet  into  the  pulp  canal.  When 
the  wood  is  withdrawn,  the  pulp  often  adheres  to  it;  if  not,  it 
may  be  quickly  and  painlessly  removed  with  a  broach.  In 
this  operation  the  immediate  paralysis  induced  renders  it  com- 
paratively painless. 

Preparation  of  the  Pulp  Canal. — After  the  removal  of  the 
pulp  the  apical  foramen  should  be  thoroughly  closed  by  any 
method  usually  employed  in  root  filling.  A  neglect  of  this  im- 
portant measure  will  greatly  endanger  the  success  of  the 
operation. 


192 


MECHANICAL    DENTISTRY, 


Fig.  So. 


The  proper  treatment  and  preparation  of  the  root  having  been 
thus  far  accomplished,  the  canal  of  the   latter  should  next  be 
enlarged  for  the  reception  of  a  dowel-pin.     This  is 
effected  with  an   ordinary  fissure  drill  or  the  Otto- 
lengui  root  reamers  (Fig.  80). 

The  natural  opening  in  the  root  should  be  enlarged 
to  the  depth  of  two  or  more  lines,  according  to  the 
length  of  the  root;  and  the  orifice  should  be  made 
large  enough  to  admit  a  support  of  sufficient  size  to 
secure  the  crown  firmly  in  position.  The  direction 
of  the  drill  in  cutting  should  follow  closely  that  of 
the  natural  canal  in  the  root,  since  but  a  slight  de- 
viation in  this  respect  may  endanger  the  integrity 
of  the  latter  by  too  great  a  thinning,  or  actual  perforation,  of  its 
walls.  The  face  of  the  root  should -then  be  given  a  suitable 
shape  for  the  reception  of  the  form  of  crown  to  be  attached,  the 
methods  of  fitting  and  inserting  which  will  now  be  considered, 
the  simple  or  all  porcelain  system  being  first  taken  up. 

Porcelain  Crowns. — The  system  of  using  all  porcelain  crowns 
has  a  number  of  advantages,  and  at  the  same  time  there  are 
strong  reasons,  we  think,  for  using  another  system — known  as 
the  ferrule  or  collar  crown — in  all  favorable  cases. 

The  porcelain  crown  is  especially  useful  where  an  inexpensive 
and  quickly  adjusted  crown  is  necessary;  or  where  some  patho- 
logical condition  would  seem  to  limit  the  probable  permanency 
of  an  operation,  or,  again,  where  a  temporary  crown  is  desired 
to  serve,  as  is  sometimes  necessary,  until  the  patient  or  operator 
can  make  suitable  engagements  for  more  permanent  work. 

The  objections  made  to  the  use  of  this  class  of  crowns  for 
permanent  work  is,  the  pin  or  post  upon  which  almost  the  en- 
tire support  of  the  crown  is  thrown  acts  as  a  lever  in  the  root 
canal,  and  sooner  or  later  many  of  the  weaker  roots  are  fractured, 
thus  ending  their  usefulness  as  a  support ;  and  again,  the  pin  or 
post,  entering,  as  it  does,  deeply  into  the  body  of  the  porcelain, 
weakens  it  at  this  point,  and  not  infrequently  do  patients  return 
with  the  crowns  fractured  through  the  center,  from  the  force  of 
mastication.  Then  again,  when  the  crowns  are  set  with  amalgam, 
which  is  the  practice  of  many,  the  discoloration  of  the  line  of 


ROOT    CROWNING. 


193 


union  with  the  root,  if  subsequently  exposed,  is  very  objection- 
able. 

The  all-porcelain  crowns  may  be  divided  into  two  classes  : 
First,  those  having  one  end  of  the  pin  or  post  baked  in  the  porce- 
lain when  the  crown  is  made,  such  as  the  Logan,  Brown,  and 
new  Richmond  ;  second,  those  attached  to  the  root  by  a  pin, 
post,  or  screw,  one  end  of  which  is  first  cemented  in  the  root 
and  the  other  afterward  to  the  crown.  Of  this  class  we  have 
the  Bonwill,  How,  Gates,  Foster,  and  Howlaiid. 

After  deciding  upon  the  form  of  crown  to  be  used,  one  should 
be  selected  to  correspond  as  nearly  as  possible  in  size  and 
general  configuration  with  its  fellow  on  the  opposite  side,  and 
to  harmonize  in  color  with  those  immediately  adjoining.  The 
manner  of  preparing  and  adjusting  each  of  the  crowns  named 
will  be  taken  up  in  the  order  given. 

The  Logan  Crown, — The  Logan  crown,  invented  by  Dr.  M. 
L.  Logan,  is  probably  of  all  these  the  one  most  extensively 
used.  The  method  of  adjusting  and  mounting  is  given  in  all  its 
details  in  the  following  article  by  Dr.  W.  S.  How  : — 

"  Fig.  86  shows  a  superior   right  central  root,  an  end  appear- 


FlG.  81. 


Fig.  82. 


Fig.  8q 


Fig.  84. 


Fig.  85. 


ance  of  the  same,  and  a  Logan  crown,  front  view.  Fig, 
87  exhibits,  at  a  '  right  angle  to  the  plane  of  the  first 
figure,  the  same  root,  its  end,  and  the  Logan  crown,  side 
view.  In  both  figures  the  root-canal  is  supposed  to  have 
been  first  drilled  to  a  gauged  depth  with  an  engine  twist- 
drill.  No.  154,  and  then  enlarged  by  means  of  a  fissure-bur, 
13 


194 


MECHANICAL    DENTISTRY. 


No.  70,  to  the  tapering  form  shown  ;  the  walls  being  subsequently 
grooved  with  an  oval  bur,  No.  90.  The  enlarged  section  (Fig.  88) 
shows  the  crown  adjusted  on  the  root  by  means  of  cement  or 


Fig. 


Fig.  87. 


Fig.  88. 


Fig.  89. 


Fig.  90. 


Fig.  91. 


Fig.  92.       Fig.  93. 


Fig.  95. 


Fig.  96, 


Fig.  97. 


gutta-percha,  which  surrounds  the  post  and  fills  all  the  spaces  in 
the  root  and  crown.  Fig.  89  shows  the  completed  crown.  Fig.  90 
exhibits  a  bifurcated    bicuspid    root,  its  end  appearance,  and  a 


ROOT    CROWNING.  1 95 

Logan  crown  adjusted  to  the  root.  Fig.  91  illustrates  the  best 
manner  of  bending  the  post.  Fig.  92  shows  a  split  post,  and  its 
adaptation  to  a  bifurcated  bicuspid  root  is  seen  in  Fig.  93.  Figs. 
94  and  95  exhibit  the  mode  of  mounting  the  Logan  crown  on  a 
superior  molar  root,  and  Figs.  96  and  97  the  same  crown  in  its 
relations  to  an  inferior  molar  root. 

"The  preceding  figures  clearly  present  to  the  mind's  eye  of 
the  expert  dentist  the  essential  features  of  the  Logan  crown  and 
the  method  of  mounting  it. 

"  The  details  are  as  follows  :  In  every  instance  where  a  root  is 
deemed  ready  to  receive  its  filling,  it  should  first  be  measured 
through  its  canal  from  the  cervical  opening  to  the  apical  foramen, 
and  this  may  be  accurately  done  with  a  gauge  adjustable  on  a 
delicate  canal-explorer  (Fig.  81).  The  same  device  serves  to 
measure  the  distance  from  the  apex  to  which  the  canal  should 
then  be  filled  (Fig.  82).  It  also  gauges  the  depth  to  which  the 
drill  may  be  carried.  The  proper  degree  of  enlargement  from 
the  bottom  of  the  drilled  hole  will,  of  course,  depend  on  the  ob- 
served size  and  character  of  the  root.  Every  dentist  should 
familiarize  himself  with  generic  tooth-forms,  so  that  when  the 
length  of  an  incisor,  cuspid,  or  other  tooth-root  is  known,  he 
can  so  nearly  determine  its  hidden  outlines  as  to  form  with  pre- 
cision a  corresponding  enlargement  of  the  root-canal,  such  as  is 
shown  by  the  several  cuts.  For  preparing  the  roots,  the  Ottolengui 
root-reamers  and  facers  (see  pages  190  and  192)  are  very  desirable 
instruments.  The  reamers  are  made  in  three  sizes  to  corre- 
spond with  the  Logan  pins.  With  a  root-reamer  of  the  appro- 
priate size,  the  root-canal  is  enlarged  to  fit  the  pin  along  its  whole 
length,  and  so  hold  the  crown  firmly,  independent  of  the  cement. 
With  a  root-facer  a  labial  slope  is  given  to  the  root-end,  so  that 
the  crown  neck  shall  fit  under  the  edge  of  the  gum.  Fig.  98 
shows  the  method  and  its  result,  and  the  cross-section  shows 
how  the  cement  incases  the  pin.  The  suitable  preparation  of  the 
bifurcated  roots  of  some  bicuspids  and  of  all  the  molars  is  a 
matter  involving  difficulties  of  an  unusual  character  and  requir- 
ing good  judgment.  The  feasibility  of  splitting  the  post  of  a 
Logan  crown  to  adapt  it  to  the  bifurcated  root  of  a  bicuspid  is 
shown  in  Figs.  92  and  93.     This  example  directs  attention  to  the 


196 


MECHANICAL    DENTISTRY. 


peculiar  shape  of  the  post,  in  which  there  is  effected  such  a 
distribution  of  the  metal  that  its  greatest  strength  is  in  the  line 
of  the  greatest  stress  that  will  in  use  be  brought  to  bear  on  the 
crown,  while  the  least  metal  is  found  at  the  point  of  the  least 
strain;  the  applied  part  of  the  post  being  in  outline  nearly  cor- 
respondent to  that  of  the  root  itself  The  root-canal  is  likewise 
conformably  enlarged  to  receive  the  largest  and  stiffest  post 
which  the  size  and  shape  of  the  root  will  permit. 


"  The  fitting  of  a  Logan  crown  to  a  root  may  be  done  with  a 
wet  stump-wheel  in  the  engine  hand-piece.  A  safe-side  crown 
corundum-wheel  (Fig.  99)  can  be  used  in  the  same  manner.  It 
also  affords  the  greatest  facility  for  the  slight  touches  required 
to  abrade  the  thin  cervical  borders  of  the  crown,  which  may  by 
this  means  be  done  without  encroachment  on  the  post. 

"  By  the  old  method  of  adapting  pivot-teeth  to  roots,  the 
close  fitting  of  the  crown  precluded  the  use  of  a  plastic  packing, 
because  its  thinness  over  the  surface  of  the  joint  made  the  pack- 
ing liable  to  break  loose  under  the  shock  and  strain  of  use.  The 


ROOT    CROWNING. 


197 


recess  in  the  Logan  crown  obviates  this  defect  by  providing  a 
receptacle  for  a  considerable  interior  body  of  cement  that  will 
be  deep  enough  to  be  self-sustaining  internally,  and  yet  allow  the 
peripheral  portions  of  the  root  and  crown  to  approach  each 
other  so  closely  that,  though  only  a  film  of  packing  remain,  it 
will  still  be  strong  enough  to  insure  the  persistent  tightness  of 
the  joint.  This  annular  boss  if  formed  of  amalgam  also  adds 
strength  in  some  cases  to  the  mount. 

"  When  enough  of  the  natural  crown  remains,  it  is  well  to 
leave  standing  some  of  the  palatal  portion,  and  cut  the  root  under 
the  gum-margin  at  only  the  labial  part,  as  shown  by  Fig.  83. 


Fig.  99. 


Fig.  100. 


The  safe-side  crov/n  wheel  is  especially  useful  in  such  cases 
(Fig.  100).  Thus  the  labial  joining  of  the  root  and  crown  will 
be  concealed,  and  the  other  parts  of  the  joint  will  be  acces- 
sible for  finishing  and  keeping  clean  (Fig.  84).  The  Logan 
crown  may  be  ground  until  a  large  part  shall  have  been  re- 
moved for  adaptation  to  the  occluding  tooth  or  teeth  without 
seriously  impairing  its  strength  (Fig.  85).  This  crown  also  in 
such  cases  maintains  the  translucency,  which  is  one  of  its  pecu- 
liar excellences,  owing  to  its  solid  porcelain  body  and  the  ab- 
sence of  a  metallic  backing  or  an  interior  largely  filled  with 
cement  or  amalgam. 

"  The  distal  buccal  root  of  the  natural  superior  molar  is  nearly 
always  too  small  to  receive  a  post  of  any  useful  diameter,  and 
therefore  the  Logan  superior  molar  crown  has  but  two  posts, 
which,  like  those  of  the  inferior  molar  crown,  are  square,  and  thus 


198 


MECHANICAL    DENTISTRY, 


may  be  easily  barbed,  as  may  also  the  ribbed  posts  of  the  crowns 
for  the  anterior  tooth-roots.  These  posts  are  large  enough  in 
all  the  Logan  crowns  to  answer  in  any  given  case,  and  can,  of 
course,  be  easily  reduced  to  suit  thin  or  short  roots. 

"  Any  of  the  cements  or  amalgams  may  be  used  in  fixing 
these  crowns,  but  good  gutta-percha,  softened  at  a  low  heat  and 
quickly  wrapped  around  the  heated  crown-post,  which  is  at 
once  seated  in  the  root,  forms  the  best  mounting  medium,  and 
has  the  great  advantage  of  permitting  a  readjustment,  or,  if 
need  be,  the  ready  removal  of  the  crown  by  grasping  it  with  a 
pair  of  hot  pliers  or  forceps,  and  holding  it  until  the  gutta-percha 
is  sufficiently  softened." 

The  Brown  Crown. — This  crown,  invented  by  Dr.  E.  Parmley 


Fig.  ioi.  Fig.  102.  Fig.  103. 


Fig.  104. 


Brown,  is  shown  in  Figs.  loi  to  104.  Fig.  loi  gives  a  lateral 
view  of  a  porcelain  crown,  with  an  iridio-platinum  pin  baked  in 
position.  The  pin  has  great  strength  at  the  neck  of  the  tooth, 
where  the  strain  is  heaviest,  and  this  strength  is  further  increased 
by  extending  the  porcelain  up  on  to  it,  as  shown  in  the  accom- 
panying illustrations. 

A  front  view  of  the  same  crown  is  illustrated  in  Fig.  102. 
The  dotted  lines  show  the  shape  of  the  pin  and  the  position 
which  it  occupies  in  the  crown. 

The  pin  is  flattened  laterally,  affording  a  strong  hold  in  the 
porcelain  without  bringing  it  too  near  the  surface  in  thin  teeth, 
while  it  also  permits  alteration  of  the  palatal  surface  of  the 
crown  in  a  close  "bite"  without  risk  of  weakening  the  body. 

Fig.  103  is  a  view  of  the  bicuspid  crown,  in  which  two  pins 
are  provided,  one  for  each  root  of  two-rooted  bicuspids. 

Fig.  104  is  a  view  of  the  same  crown  with  the  two  pins  pressed 


ROOT    CROWNING.  I99 

together,  forming  a  single  pin  of  great  strength  for  a  single-rooted 
bicuspid. 

The  double  pin  in  the  bicuspids  prevents  the  gradual  loosen- 
ing of  the  crown  by  the  rotary  movement  of  the  jaws  in  mastica- 
tion, which,  acting  on  the  two  cusps,  exerts  such  leverage  as  to 
sometimes  turn  and  break  down  ordinary  crowns  where  only  one 
pin  is  used. 

The  roots  are  ground  concave  to  fit  the  crowns  with  corun- 
dum-points or  a  Willard  countersink  bur,  and  close  joints  are 
made  well  under  the  gum,  the  pins  being  set  with  oxyphosphate 
cement.  The  canal  should  be  enlarged  just  enough  to  admit 
the  pin,  which  should  fit  snugly  throughout  its  entire  length,  the 

Fig.  105.  Fig.  106.  Fig.  107. 


better  to  distribute  the  leverage  exerted  by  the  crown,  and  thus 
directly  to  increase  the  strength  of  the  attachment. 

The  New  Richmond  Crown. — Dr.  George  Evans,  in  his  trea- 
tise on  "  Crown  and  Bridge  Work,"  describes  the  new  Richmond 
crown  as  follows  :  To  illustrate  and  describe  the  method  of 
mounting  this  crown,  a  superior  left  central  incisor  root  will 
serve  as  a  typical  case,  and  its  projecting  end  is  to  be  shaped 
as  seen  in  Figs.  105  and  ig6-  This  can  be  rapidly  done  with  a 
narrow,  safe-sided  flat  or  square  file,  the  angles  of  the  slopes 
being  such,  that  the  gum  on  the  labial  and  palatal  aspects  will 
not  interfere  with  nor  be  disturbed  by  this  preliminary  work,  as 
the  root-end  is  not,  in  this  operation,  to  be  cut  quite  down  to  the 
gum.  An  Ottolengui  root-reamer  No.  2  is  then  employed  to 
bore  out  the  root  to  receive  the  crown-post,  which  is  of  the  same 
size  and  shape  as  the  Logan  crown-post  for  a  central  incisor. 

The  sectional  view  (Fig.  107)  shows  the  relation  of  the  reamer 


200 


MECHANICAL    DENTISTRY. 


to  the  root.  The  new  Richmond  crown  (Fig.  io8)  is  then  tried 
on  the  root  (Fig.  109),  and  its  position  relative  to  the  adjacent 
and  occluding  teeth  noted.  If  the  cutting-edge  of  the  crown  is 
to  be  brought  out  for  alignment  with  its  neighbors,  the  root  can 
be  drilled  a  little  deeper,  and  the  reamer  pressed  outward  as  it 
revolves  to  cut  the  labial  wall  of  the  cavity.  The  palatal  root- 
slope  must  then  be  filed  to  make  the  V  correspond  to  the 
changed  inclination  of  the  crown. 

Thus,  by  alternate  trial  and  reaming  and  filing,  the  crown  may 
be  fitted  to  the  root  and  adjusted  in  its  relations  until  the  post 
has  a  close,  solid  bearing  against  the  labial  and  palatal  walls  of 
the  enlarged  pulp-chamber,  and  the  crown-slopes  are  separated 
from  the  root-slopes  by  the  thickness  of  a  sheet  of  heavy  writing- 


FiG.   108. 


Fig.  109. 


paper.  This  space  can  be  accurately  gauged,  and  the  root-slopes 
conformed  to  the  crown-slopes  by  warming  ^he  crown  and  put- 
ting on  its  slopes  a  little  gutta-percha,  so  that  an  impression  of 
the  root-end  may  be  taken,  and  the  root-slopes  dressed  with  a 
file  until  the  film  of  gutta-percha  proves  to  be  of  equal  thinness 
on  both  slopes. 

To  permanently  attach  the  crown.  Dr.  Richmond  usually  takes 
a  thin,  perforated  disk  of  gutta-percha,  pushes  the  post  through 
it,  warms  the  crown,  presses  it  into  place,  and  when  cooled 
removes  it,  and  with  a  sharp  knife  trims  away  the  gutta-percha 
close  to  the  crown-neck.  He  then  warms  the  crown,  puts  a  very 
little  oxyphosphate  cement  on  the  post,  and  presses  the  crown 
home.     Fig.  iio  shows  the  completed  crown. 

The  obvious  advantages  of  the  device  are  the  readiness  with 
which  the  slopes  of  the  root-end  maybe  shaped  with  a  file  ;  the 


ROOT    CROWNING. 


20 1 


facility  with  which  these  slopes  may  be  given  any  angle  to  set 
the  crown  out  or  in  at  the  base  or  at  the  cutting-edge,  or  to  give 
it  a  twist  on  its  axis;  the  certainty  that,  once  adjusted,  the  final 
setting  will  exactly  reproduce  the  adjustment;  the  assurance 
that  in  use  the  crown  will  not  be  turned  on  its  axis,  a  most 
common  cause  of  the  loosening  of  artificial  crowns  ;  the  firmness 
of  its  resistance  to  outward  thrust  in  the  act  of  biting.  This  is 
made  apparent  by  Fig.  iii,  wherein  it  will  be  seen  that  in  an 
outward  movement  the  crown  B  would  rock  upon  A  as  a  pivot. 
The  dotted  line  D  shows  how  the  crown-slope  is  resisted  by  the 
root-slope,  which  extends  so  far  toward  the  incisive  edge  that  a 
much  firmer  support  is  given  to  the  crown  than  if  the  resistance 
should  be,  as  it  usually  is,  on  the  line  of  the  gingival  margin  C. 


Fig.  112. 


Fig.  113. 


Fig.  114. 


For  roots  that  have  become  wasted  below  the  gum-surface  it 
is  not  suitable,  except  in  such  cases  as  are  decayed  under  the 
labial  or  palatal  gum-margin  only,  but  have  yet  projecting  the 
approximal  portions  of  the  crown  (Fig.  112). 

The  sectional  view  (Fig.  1 13),  and  the  perspective  plan  views 
(Fig.  114)  illustrate  the  manner  of  mounting  these  crowns  on 
this  class  of  roots.     The  finished  crown  appears  as  in  Fig.  114. 

The  cases  for  which  this  crown  seems  specially  adapted  are 
such  as  have  some  considerable  portion  of  the  natural  crown 
remaining. 

The  Bon  will  Crown. — This  was  one  of  the  first  crowns 
introduced  in  improved  porcelain  crown-work.  The  process  of 
its  adjustment  and  insertion  is  explained  in  a  lengthy  article  by 
its  inventor,  Dr.  W.  G.  A.  Bon  will,  from  which  the  following  is 
presented  : — 


202 


MECHANICAL    DENTISTRY. 


"  These  all-porcelain  crowns  have  three  distinctive  features  : 
a  concave  or  countersunk  base  ;  a  triangular  opening  from  the 
base  to  a  point  at  or  near  the  cutting-edge  of  the  incisors,  the 
base  presenting  to  the  labial  surface  (at  its  upper  portion  this 
groove  is  enlarged) ;  a  peripheral  margin  or  border  resting  per- 
fectly flat  on  the  root,  the  concavity  of  the  base  on  the  palatal 
side  being  at  a  much  more  acute  angle  than  on  the  approximal 
sides.     An  anchorage  is  made  in  the  incisors  by  a  depression  or 

Fig.  115.     Fig.  116.      Fig.  117.  Fig.  118.       Fig.  119.      Fig.  120.     Fig.  121. 


"Fig.  115. — Sectional  view  of  an  incisor  crown  from  mesial  side,  showing  the 
undercut  at  the  point  opening  on  palatal  surface,  the  conical  base,  and  the  opening  of 
the  same  to  the  retaining-grocves,  with  the  exact  relations. 

"  Fig.  116. — Palatal  view  of  same  tooth,  a  is  the  external  opening  for  egress  of 
alloy  and  for  packing  around  the  pin.  The  dotted  lines  show  the  recess  or  undercut 
on  the  mesial  and  distal  sides  and  near  the  point  for  retaining  the  crown,  and  its  rela- 
tion with  the  conical  base. 

"  Fig.  117. — Grinding-surface  view  of  a  superior  molar  with  the  countersunk  pin- 
holes on  the  buccal  and  palatal  sides. 

"Fig.  118. — Same  view  of  an  inferior  molar  with  the  pin-holes  on  the  mesial  and 
distal  sides. 

"Figs.  119  and  120. — Sectional  views  of  a  molar  and  a  bicuspid  crown,  showing 
the  countersinks  and  their  relations  with  the  conical  base. 

"Fig.  121. — Sectional  view  of  an  incisor  root,  showing  the  retaining-cuts  made  by 
the  wheel-bur  shown  in  Fig.  128." 


undercut  between  the  labial  and  palatal  surfaces,  opening  on  the 
latter.  In  the  bicuspids  and  molars  the  retaining-pits  are  nearer 
the  grinding-surface. 

"  The  concave  base  of  the  crown  prevents  the  amalgam  from 
escaping  under  the  heavy  pressure  exerted  to  force  it  into  posi- 
tion, and  in  impacting  the  amalgam  and  expressing  the  mercury. 
It  allows  of  a  dense  body  of  material  around  the  metallic  pin, 
giving  the  equivalent  of  a  pin  the  whole  diameter  of  the  base  of 
the  crown.  It  leaves  no  joint,  the  crown  and  root  being  contin- 
uous.    The  amalgam    is  so  thoroughly  hardened   at   once   by 


ROOT    CROWNING. 


20  ■ 


impaction  in  the  double  concave  of  crown  and  root  as  to  make 
a  very  firm  operation.  It  prevents  any  possibility  of  the  crown's 
twisting  upon  the  pin  and  root.  In  the  event  of  fracture  of  the 
crown,  the  convex  surface  of  amalgam  on  the  root  makes  the 
substitution  of  a  new  crown  an  easy  operation.     It  enables  the 


Fig.  122.  Fig.  124.        Fio.  125 

4M  ^^ 


Fig. 
Fig.   126.  Fig.  127.       128. 


Fig.  12.^. 


"  Fig.  122. — End  view  of  a  canal  prepared  for  the  improved  combination-metal  pin. 

"  Fig.  123. — End  view  of  same  canal  as  in  Fig.  122,  prepared  for  a  triangular  pin, 
showing  how  much  more  of  the  mesial  and  distal  surface  have  been  cut  away  from 
it  than  in  Fig.  122  for  the  improved  pin. 

"Fig.  124. — Sectional  view  of  an  incisor  crown  and  root,  with  the  improved  pin 
in  its  relative  position  to  each,*  with  the  depressions  made  by  wheel-bur. 

"Fig.  125. — Sectional  view  of  a  superior  molar,  with  the  large  angular  pin  in 
palatal  root  and  two  square  pins  in  the  buccal  roots,  one  being  shorter  and  not  passing 
through  the  crown. 

"  Fig.  126. — Block  of  a  molar  and  bicuspid,  showing  the  countersunk  holes  for  pins 
in  the  molar,  and  the  hole  in  the  mesial  side  of  the  second  bicuspid  where  a  pin  is 
alloyed  in  and  set  into  a  decayed  cavity  in  the  distal  surface  of  the  first  bicuspid, 
being  held  upon  the  molar  roots  and  attached  to  the  bicuspid  by  the  alloy. 

"  Fig.  127. — Side  and  end  view  of  the  largest-size  angular  combination-metal  pin 
with  the  stamped  serrations  f  The  .square  pins  are  without  serrations  and  double- 
pointed,  made  of  the  same  metal  and  of  equal  thickness  throughout. 

"  Fig.  128. — The  smallest-sized  wheel-bur  for  grooving  the  canals  for  anchoring  the 
pin  and  alloy." 


*The  sectional  views  of  the  incisor  and  molar,  giving  the  relative  position  of  the 
pins  in  the  crowns  and  roots,  should  show  pins  of  larger  size.  The  pins  as  fur- 
nished should  be  filed  down  but  little.  It  is  not  absolutely  necessary  that  so  many 
serrations  should  be  made  in  the  canals  by  the  wheel-bur  for  retaining  the  amalgam 
and  pin  as  are  shown  in  the  sectioiial  view  of  the  root  of  an  incisor.  While  no  ser- 
rations are  shown  in  the  roots  of  the  molars,  it  is  understood  that  all  the  canals  must 
have  the  serrations.  The  square  pins  in  the  canals  need  no  serrations.  At  the  point 
where  they  occupy  the  countersink  in  the  crowns,  make  two  or  three  very  slight  cuts 
on  the  edges  with  a  sharp  file.     The  ends  can  be  left  blunt. 

f  These  pins  are  now  made  without  serrations.  When  amalgam  is  used  for  secur- 
ing them,  they  become  amalgamated  and  firmly  united. 


204  MECHANICAL    DENTISTRY. 

operator  to  fit  the  crown  in  much  less  time  ;  it  allows  a  proper 
position  to  be  given  to  the  pin,  with  less  danger  of  fracture  there- 
from ;  it  permits  of  a  larger  quantity  of  amalgam  in  the  crown, 
and  is  capable  of  bearing  greater  strain  ;  it  makes  the  permanent 
success  of  the  operation  probable,  from  the  fact  that  it  is  abso- 
lutely jointless,,  and  secures  immediate  solidity,  even  while  the 
amalgam  is  semi-plastic.  These  crowns  are  capable  of  resisting 
the  force  of  biting  or  mastication,  because  they  are  supported 
nearly  to  the  cutting-edge  or  grinding-surface,  the  triangular 
opening  from  the  concave  base  nearly  to  the  cutting-edge  allow- 
ing the  pin  to  be  imbedded  in  the  labial  face  of  the  crown  where 
there  is  the  greatest  amount  of  porcelain. 

"  The  amalgam  to  be  used  as  the  medium  of  union  must  set 
quickly  and  be  very  hard.  Thus  far  I  have  found  nothing 
better  than  the  alloys  I  have  specially  prepared  for  this  line  of 
work,  and,  though  they  are  costly,  the  superior  results  obtained 
by  their  use  amply  repay  the  cost.  I  use  No.  i  generally.  If 
mixed  thick,  it  will  set  so  quickly  that  the  operator  must  work 
rapidly  to  prevent  its  being  wasted.  In  incisor  cases  I  use  No. 
3  at  the  gum  line  and  make  a  close  joint. 

"  In  preparing  the  canal,  use  first  a  small-sized,  spear-shaped 
drill,  carefully  following  the  natural  channel.  Then  follow  with 
a  larger  one,  taking  care  not  to  cut  through  the  root  near  the 
apex.  On  the  mesial  and  distal  sides  cut  away  but  little,  as 
there  is  where  fractures  are  most  liable  to  occur.  The  canal  can 
be  very  tapering  and  yet  hold  the  pin.  There  need  be  but  very 
little  space  around  the  pin.  By  all  means  save  all  the  walls  of  the 
root  possible.  The  smallest-sized  wheel-bur  may  be  used  to  make 
a  thread  at  various  points  along  the  canal  to  hold  the  amalgam. 

"  If  the  patient  exposes  the  gums  much  in  speaking  or  smiling, 
the  root  may  be  cut  down  with  the  bur  or  corundum-wheel 
beyond  the  free  edge,  to  conceal  the  joint.  With  bicuspids  and 
molars  it  is  not  necessary  to  go  below  the  gum;  a  joint  well 
made  will  not  be  observed,  and  the  strength  of  the  root  will  be 
preserved.  If  the  root  is  decayed  below  the  gum,  after  removing 
the  softened  parts,  fill  it  with  alloy. 

"  It  is  not  necessary  that  the  face  of  the  root  should  be  flat ; 
it  may  be  either  concave  or  convex,  according  to  indications. 


ROOT    CROWNING.  205 

"  It  is  advantageous  to  take  an  impression  and  '  bite  '  of  the 
root,  and  make  a  model  and  articulation  in  plaster. 

"  The  crown  to  be  inserted  should  be  inspected  closely,  as  the 
retaining  undercut  in  the  incisors  and  the  depressions  in  the 
bicuspids  and  molars  may  not  be  well  defined.  If  not,  the 
crowns  are  liable  to  work  loose.  If  the  base  has  been  ground 
off  in  fitting,  the  edges  should  be  beveled  again  to  a  fine  margin 
with  a  corundum-point.  The  crown  should  be  fitted  to  the  root 
in  the  mouth,  not  to  the  plaster  cast.  The  articulation  should 
be'  clear,  to  avoid  displacement.  The  pin  should  be  as  large  as 
the  previously  prepared  canal  will  admit.  The  pin  must  in 
every  case  be  fitted,  and  in  fitting  it  file  only  on  the  plain  sides. 
Leave  the  end  sharp,  to  offer  the  least  resistance  in  passing 
through  the  amalgam.  The  end  of  the  pin  to  be  passed  into 
the  crown  needs  very  little  alteration.  The  crown,  being  open  on 
the  palatal  surface  of  the  incisors,  permits  a  blunt-pointed  pin  to 
go  up  to  its  place.  The  middle  of  the  pin  should  not  be  inter- 
fered with  if  it  can  be  avoided.  It  is  well  to  cut  the  pin  a  little 
short  for  incisors,  as  it  may  not  get  pushed  entirely  up  in  the 
root  through  the  amalgam.  Small  square  pins  are  used  in  the 
bifurcated  roots  of  bicuspids  and  in  the  buccal  roots  of  molars. 
They  can  be  sharpened  at  both  ends,  but  the  outer  end  will  not 
require  so  much  sharpening.  The  palatal  roots  of  molars  will 
generally  take  one  of  the  largest  thick  pins,  with  one  square  pin  in 
the  largest  and  most  accessible  buccal  root.  Each  canal  should 
have  a  pin,  if  the  canal  can  be  reached  and  properly  prepared  to 
receive  it,  even  though  the  pin  has  to  be  so  short  as  not  to  pass 
through  the  hole  in  the  crown.  If  it  enters  the  countersunk 
base  it  will  support  the  root.  The  lower  molars  will  require  two 
of  the  largest-sized  pins.  As  the  support  of  the  root  is  depend- 
ent upon  the  size  of  the  pin  and  the  depth  to  which  it  is 
inserted,  single-rooted  teeth  should  have  the  very  largest  thick 
pin.  If  the  root  is  thin  on  the  mesial  and  distal  sides,  the  thin, 
angular  pin  is  to  be  preferred.  Ordinarily  these  large  pins  do 
not  have  to  be  bent.  If  necessary,  it  had  better  be  done  with  a 
hammer  and  before  the  mercury  touches  them.  The  pin  should 
have  free  movement  in  both  root  and  crown.  Should  it  be  dis- 
covered that  the  pin  is  too  long  after  it  has  been  packed  in  the 


206  MECHANICAL    DENTISTRY. 

root,  it  can  be  cut  off  with  sharp  forceps,  pressing  them  up 
against  the  pin  to  prevent  displacement.  The  pin  can  be 
sharpened  subsequently  with  the  corundum-wheel. 

"To  insure  an  amalgamation  of  the  pin  with  the  filling, 
brighten  the  surface  of  the  former  before  inserting. 

"The  roots,  crown,  and  pins  being  in  readiness  and  arranged 
on  the  table,  so  that  no  mistake  may  occur  from  getting  the  pin 
in  the  wrong  position,  and  the  appliances  necessary  for  the 
operation  being  at  hand,  the  alloy  preferred  should  be  mixed  a 
little  thinner  than  if  intended  for  a  filling,  especially  where  the 
root  has  a  long  canal.  The  shorter  the  canal,  the  thicker  the 
amalgam  may  be  mixed.  Mix  only  enough  at  one  time  for  one 
root.  Put  enough  amalgam  in  the  canal  to  nearly  fill  it,  but  do 
not  pack  it ;  force  into  it  a  steel  pin  made  for  the  purpose,  of 
about  the  same  size  as  the  pin,  to  make  way  for  the  easier  inser- 
tion of  the  latter.  Then  grasp  the  pin  with  suitable  forceps,  and 
carefully  but  steadily  press  it  up  to  its  destination.  If  you  can- 
not succeed  in  doing  so,  remove  it,  and  again  use  the  steel  pin. 
When  in  place,  use  an  instrument  with  a  point  small  enough  to 
pass  between  the  pin  and  the  root,  and  pack  by  tamping  the 
amalgam  around  it.  A  piece  of  bibulous  paper  placed  over  the 
point  of  the  instrument  will  assist  materially  in  carrying  the 
amalgam  before  it.  Before  the  amalgam  has  become  too  hard, 
replace  the  crown  to  determine  that  the  pin  is  in  proper  position  ; 
if  not,  it  can  be  crowded  to  one  side  or  the  other  with  the  tamp- 
ing-tool.  Should  the  pin  be  found  to  be  rather  long,  it  can  be 
ground  off  with  the  corundum-wheel,  holding  it  meanwhile  with 
the  forceps.  No  attempt  should  be  made  to  bend  the  pin  after  it 
has  been  amalgamated,  for  fear  of  breaking  it.  If  any  amalgam 
has  been  left,  and  it  is  still  plastic,  it  may  be  packed  around  the 
pin  at  the  base  of  the  root,  using  the  bibulous  paper  as  before 
directed.  If  not,  mix  again  to  complete  the  operation.  Bank 
up  the  amalgam  on  the  root  high  enough  to  fill  the  base  of  the 
crown.  The  crown  should  now  be  tried  on,  and  forced  home 
with  an  adjuster  adapted  to  the  case,  removing  the  surplus 
amalgam  if  too  much,  or  adding  if  not  enough.  Remove  and 
dry  the  crown,  and  fill  up  simply  the  undercut  cavity  near  the 
cutting-edge  if  an  incisor,  or  the  depressions  in  the  crowns  of 


ROOT    CROWNING.  20/ 

bicuspids  or  molars,  allowing  a  very  little  to  extend  into  the 
cervical  base.  Now  force  it  home  with  the  adjuster.  It  requires 
considerable  force  to  set  one  of  these  crowns  according  to 
directions, — a  force  which  cannot  be  applied  with  a  mallet  with- 
out danger  of  loosening  or  displacing  the  crown.  Steady 
pressure  with  slight  rotation  will  carry  the  crown  into  place,  if 
the  amalgam  is  not  too  hard  or  there  is  not  too  much  of  it.  I 
would  advise  you  not  to  attempt  to  set  a  crown  without  an 
adjuster  or  its  equivalent.  Free  mercury  will  be  squeezed  out 
on  the  palatal  surface,  which  should  be  wiped  off.  Now  hold 
the  crown  in  place  with  the  fingers,  with  the  bibulous  paper 
under  the  tamping-instrument,  and  consolidate  the  amalgam 
around  the  point  of  the  pin  in  the  crown,  absorbing  any  free 
mercury  which  appears  there.  The  excess  of  alloy  at  the  joint 
must  now  be  removed,  care  being  taken  to  press  the  crown  up 
while  this  is  being  done.  The  amalgam  packed  around  the  pin 
in  the  crown  on  the  palatal  side  should  be  as  stiff  as  may  be  to 
work  readily.  It  is  well  to  leave  over  some  of  the  first  mixing 
for  holding  the  pin,  and  this  will  be  about  right  for  consolidat- 
ing about  this  point. 

"  If  in  a  bicuspid  or  molar  crown  the  pin  should  come  so  far 
through  as  to  interfere  with  articulation,  it  may  be  ground  off 
with  the  corundum-wheel  while  the  crown  is  firmly  held. 

"The  case  can  now  be  dismissed,  with  directions  for  the 
patient  to  return  the  next  day,  in  order  to  make  sure  that  the 
articulation  is  correct  and  to  dress  off  the  joint  between  the  crown 
and  root,  which  may  be  done  with  a  small,  round-headed  bur. 

"  There  are  some  cases  in  which  the  root  cannot  be  filled  with 
anything;  if  in  a  molar,  the  pulp-chamber  can  be  relied  upon  to 
hold  a  headed  pin  or  pins.  When  a  tap-hole  is  required  in  the 
root  it  can  be  made  low  down  and  at  an  acute  angle,  and  the 
amalgam  packed  around  the  root-canal  above  the  tap. 

"  Should  an  artificial  crown  be  broken,  another  can  easily  be 
substituted  by  burring  off  any  excess  of  amalgam,  and  using 
fresh  amalgam,  mixed  thin,  to  allow  of  ready  adjustment. 

"  Two  crowns  can  be  inserted  on  the  root  of  one  large  molar 
with  the  assistance  of  the  decayed  approximal  surface  of  an 
adjacent  tooth  (see  Fig.  126)." 


2o8 


MECHANICAL    DENTISTRY, 


The    How  Crowns  and  Methods. — These  crowns  are  the 
invention  of  Dr.  W.  Storer  How.     There  are  two  styles, — -foiir- 
pin  crowns  for  incisors,  cuspids,  and  bicuspids,  and 
9- porcelain  dovetail  crozvns  iox  bicuspids  and  molars.    ^^^^ 
Each   form    embraces   some    novel    features.     Dr. 
How's  methods,  being  general  in  application,  arc 
used  in  inserting  other  forms  of  crowns. 

The  following  are   Dr.  How's   descriptions  and 
illustrations  of  his  methods  and  crowns  : — 

Pig.  130.        Fig.  131.  Fig.  132.  Fig.  133.    Fig.  134.  Fig.  135. 


"  The  Four-Pin  Crown. — The  difficulties  and 
uncertainties  in  mounting  artificial  tooth-crowns 
on  roots,  by  either  old  or  new  methods,  led  me  to 
a  careful  study  of  the  problem,  and  resulted  in  a 
nearly  simultaneous  devising  of  several  new  forms 
of  crowns  and  appliances  for  setting  them,  as  well 
as  a  perfected  method  of  performing  the  operation 
of  fixing  a  peculiar  screw-post  (Fig.  130)  in  a  root, 
and  also  a  novel  process  of  attaching  the  crown 
to  the  post.  At  present  I  will  describe  simpl\' 
the  four-pin  crown  (Fig.  131)  and  the  successive 
steps  to  be  taken  in  mounting  it. 

"  I.  When  the  root    is  in  proper    condition  for 
mounting,   measure    the    depth    of    the    canal    by 
means  of  the  canal-plugger  and  its  flexible  gauge 
(Fig.  129),  and  fill  the  canal  at  and  a  short  distance  from 
the  apex  of  the  root,  keeping  the  gauge  at  position  to 


ROOT    CROWNING. 


209 


show  the  full  length  of  the  canal  and  also  the  distance  to 
which  it  has  been  filled. 

"  2.  Cut  off  the  root-crown  with  excising  forceps  and  a  round 
file,  down  to  the  gum-margin,  and  with  barrel-bur  No.  241  cut 
the  labial  part  of  the  root  fairly  under  the  gum  without  wound- 
ing it. 

"3.  Set  gauge  on  a  Gates  drill  (Fig.  136)  to  one-half  the 
gauged  depth  of  the  canal,  and  drill  to  that  depth. 

"4.  Set  the  twist-drill  in  its  chuck  (Fig.  132)  to  project  the 


Fig.  137, 


Fig.  141. 


same  length  as  the  Gates  drill,  and  drill  the  root  to  exactly  that 
depth, 

"  5.  Enlarge  the  mouth  of  the  canal  one-sixteenth  of  an  inch 
deep  all  around  to  near  the  margin  of  the  root,  as  shown  in  Fig. 
133,  using  square-end  fissure-bur  No.  59,  and  then  with  oval, 
No.  94,  undercut  a  groov-e  lingually  and  at  the  sides. 

"  6.  If  the  rubber-dam  is  to  be  used  for  a  gold  or  plastic 
backing,  put  it  now  over  the  root  with  Hunter's  root-clamp,  also 
over  the  adjacent  teeth,  and  thoroughly  dry  the  canal. 

"  7.  Set  the  tap  in  its  chuck  (Fig.  134)  a  trifle  less  in  length 
than  the  drill,  oil  it,  and  carefully  tap  the  root  to  the  gauged 
depth. 

14 


2IO  MECHANICAL    DENTISTRY. 

"  8.  Insert  the  post  in  its  chuck  (Fig.  135)  to  the  exact  gauge 
of  the  tap,  and  turn  the  thumb-screw  down  hard  on  the  end  of 
the  post,  then  screw  the  post  into  the  root,  release  the  thumb- 
screw, unscrew  the  chuck  a  half-turn,  bend  the  post  until  the 
chuck  stands  in  center  line  with  the  adjoining  teeth,  and  unscrew 
the  chuck  from  the  post. 

"  9.  Slit  the  rubber  back  from  adjacent  teeth,  tucking  the 
flaps  out  of  the  way  so  that  the  occlusion  may  be  tried,  the  post 
excised  and  ground  off  until  the  teeth  close  clear  of  the  post. 

"  10.  Try  the  crown  on  the  post,  and  with  disk  grind  the 
rib  between  the  neck-pins  until  the  crown  is  labially  flush  with 
the  root-margin,  using  the  disk  dry  and  cutting  a  little  at  a  time 
until  exactly  flush. 

"11.  Take  the  crown  and  place  the  mandrel  (Fig.  137)  between 
the  pins  just  as  the  post  is  to  be,  and  with  the  pliers  (Fig.  138) 
bend  the  pins  carefully  over  the  mandrel,  cutting  off  the  pins  if 
too  long  to  be  pinched  in  on  the  mandrel  at  the  sides,  observing 
that  the  pin  nearest  the  cutting-edge  is  first  to  be  bent  (Fig.  139), 
and  the  opposite  pin  bent  bclozv  it  on  the  mandrel,  and  so  with 
the  others  (Fig.  140). 

"  12.  Slip  the  crown  over  the  post,  try  occlusion,  and  with 
the  post-chuck  bend  the  post  until  the  crown  is  properly  aligned 
with  the  teeth,  then  with  a  stump  corundum-wheel  No.  3  grind 
the  neck  of  the  crown  to  a  close  labial  fit  with  the  root,  fitting 
only  the  portion  to  be  concealed  by  the  gum,  leaving  narrow 
gaps  at  the  sides  to  be  filled  by  the  backing  between  crown  and 
root  (Fig.  141). 

"  13.  Grind  cutting-edge  for  occlusion  and  relation  to  the 
other  teeth,  and  be  sure  that  the  opposing  tooth  does  not  strike 
the  crown,  the  post,  or  the  pins. 

"  14.  Fix  the  crown  on  the  post  by  pinching  the  pins  into  the 
screw-threads  in  the  post  with  the  special  pliers  for  that  purpose. 

"15.  Finally,  pack  the  backing  of  gold,  or  cement,  or  amal- 
gam, or  Wood's  metal,*  or — for  temporary  backing  while  treat- 
ing abscess — gutta-percha,  into  all  the  crevices  around  the  post 
and  behind  and  under  the  pins,  and  between  the  crown  and  the 

*  Wood's  metal  suggested  by  Prof.  J.  Taft. 


ROOT    CROWNING. 


211 


root;  contour  and   finish  thoroughly,  so  that  no  ledge  or  other 
imperfection  can  be  found. 

"  Fig.  142    shows   in    vertical   mid-section   an   incisor    crown 
mounted   on   a   root ;    the   blackened   portions   of  the   backing 


Fig.  142. 


Fig.  143. 


&^>1;- 


Fig.  144. 


I.  '%^  „nf5'''  >^ 


^";l<^ 


serving  to  define  clearly  the  locking-hold  of  the  backing  on  the 
screw-post,  the  crown-pins,  and  the  root  recess. 

"  Fig.  143  shows  in  perspective  a  cuspid  crown  ready  to  be 
slipped  over  its  post,  and  also  a  cuspid  crown  ready  for  its  post 
in  the  bicuspid  root,  which  has  its  lingual  cusp  remaining ;  and 


Fig.  145. 


Fig.  146. 


Fig.  147. 


Fig.  144  shows  these  crowns  on  their  posts  awaiting  the  com- 
pleting or  contour-backing. 

"  When  it  is  desired  to  contour  the  backing  of  a  cuspid  crown 
to  form  an  inner  cusp,  or  to  adapt  a  cuspid  or  incisor  crown  for 
masticating  uses,  the  pins  may  be  twisted  together  over  the 
mandrel,  and  again  twisted  tightly  over  the  post,  as  in  Fig.  145  ; 
but  in  some  cases  it  may  be  better  to  bend  the  neck-pins,  as  in 
Fig.  146,  instead  of  twisting  them.     In  all  cases  the  bent  pins 


212 


MECHANICAL    DENTISTRY, 


are  to  be  pinched  quite  hard  over  the  mandrel  and  post,  so  that 
the  serrations  of  the  pliers  will  roughen  the  pins  to  prevent  their 
being  pulled  through  the  backing,  which  should  also  be  carefully 
condensed  around  the  pins  and  post. 

"  When  the  root  is  much  decayed,  the  bottom  of  the  cone- 
shaped  cavity  may  be  drilled  and  tapped  to  the  depth  of  a  six- 
teenth of  an  inch,  and  the  post,  thus  anchored,  may  be  further 
secured  by  cement  in  the  grooved  walls  of  the  cavity  and  around 
the  post  (Fig.  147). 

"The  screw-posts  are  made  of  crown-metal,  an  alloy  devised 
for  the   purpose  in  order  to  obtain  a  stiff  post  that  will  permit 


Fig.  I 


Fig.  149.  Fig.  150. 


Fig.  151. 


Fig.  152. 


the  cutting  of  the  peculiar  and  extremely  accurate  thread  formed 
upon  it,  and  which  will  not  amalgamate  or  be  otherwise  affected 
by  any  backing  material  that  may  be  used.  Of  course,  platinum 
or  platinum  alloyed  with  iridium  may  be  employed  for  posts, 
but  the  crown  metal  is  in  every  way  superior. 

"  There  are  some  cases  of  a  class  which  has  hitherto  presented 
difficulties  that  may  now  be  easily  overcome  by  grinding  the 
post  flat  on  the  crown  side  after  it  has  been  set  and  bent  in  the 
root  (Fig.  148),  so  as  to  be  clear  of  the  occluding  tooth;  and 
then  the  crown-pins  may  be  bent  over  the  reduced  post,  the 
crown  fitted  and  ground  to  clear  the  opposing  tooth  (Fig.  149), 
and  the  backing  added  in  completion. 

"  A  similar  case,  in  which  the  opposing  tooth  and  a  proper 


ROOT    CROWNING. 


213 


alignment  require  an  oblique  bending  of  the  pins,  is  seen  in  Fig. 
150,  while  the  reverse  arrangement  of  parts  is  shown  in  Fig.  151. 
The  crown  is  thus  seen  to  be  adapted  to  a  wide  range  of  adjust- 
ments, because  its  point  of  contact  with  the  root  is  at  the  labial 
portion  of  the  neck,  on  which,  as  on  a  hinge,  the  crown  may  be 
swung  out  or  in  (Fig.  152,  dotted  lines),  over  an  arc  of  at  least 
sixty  degrees,  at  any  point  of  which  it  may  be  quickly  and  firmly 
fixed.  The  labio-cervical  junction  is  made  just  under  the  gingi- 
val margin,  and  I  usually  interpose  a  thin  layer  of  cement,  amal- 
gam, or  gutta-percha,  or  a  narrow  ribbon  or  several  large  blocks 
of  soft  gold;  the  joint  always  to  be  made  carefully  smooth,  and 
hid  from  view  under  the  free  margin  of  the  gums." 

The  Porcelain  Dovetail  Tooth-Crown. — These  crowns  are 


Fig.  153.       Fig.  154.  Fig.  155.  Fig.  156.       Fig.  157.  Fig.  158. 


designed  for  the  roots  of  bicuspids  and  molars  only,  and  the 
process  of  mounting  them  may  be  very  briefly  described. 

"  Fig.  153  shows  the  roots  of  an  inferior  molar  after  the  apical 
portions  have  been  filled,  the  neck  recessed,  the  canals  drilled 
and  tapped,  and  two  How  screw-posts  firmly  fixed  therein,  the 
ends  of  the  posts  having  been  pinched  toward  each  other  by 
means  of  a  pair  of  pliers,  so  that  they  will  go  through  the  cen- 
tral opening  in  the  crown  (Fig.  154).  This  opening  is  of  a  dove- 
tail form,  as  shown  in  cross-section  by  Fig.  155,  where  the  crown 
is  seen  in  place  over  the  posts  on  the  root.  It  is  thus  made 
obvious  that  the  crown  may  be  easily  put  on  and  off  the  root  in 
the  process  of  fitting  the  crown-neck  to  the  root-neck,  and  also 
that,  for  occlusion,  the  crown  may  be  ground  low  on  any  or  all 
sides  without  destroying  the  dovetail  function  of  the  central 
cavity.  When  the  fitting  is  completed,  and  the  crown  cut  so 
short  as  to  be  3^2"  of  ^^   i^ch   distant  from  the  occluding  tooth, 


214 


MECHANICAL    DENTISTRY. 


amalgam  is  packed  into  the  neck  recess,  around  the  posts,  and 
thinly  over  the  cervical  margin  of  the  root,  the  crown  put  in 
place,  and,  with  thumb  pressure,  firmly  seated.  Then  test  the 
occlusion,  and  complete  the  operation  by  packing  amalgam  into 
the  crown  opening,  which  will  permit  the  forcing  of  the  amalgam 
in  all  directions,  to  insure  a  firm  base  for  the  crown  and  its 
secure  dovetail  attachment  to  the  posts,  as  shown  by  Fig.  155. 

"  The  bicuspid  crown  (Figs.  156  and  157)  is  similarly  mounted, 
as  may  be  seen  in  Fig.  158,  cross-section  ;  the  same  crown  and 
root  being  shown  in  contour  by  Fig.  159.  In  some  instances 
this  bicuspid  crown  may,  like  the  Foster  crown,  be  secured  by 
a  headed  screw,  as  shown  in  Fig.  160.  The  root  having  been 
drilled  and  tapped  and  recessed,  and  the  crown  properly  fitted 


Fig.  159. 


Fig.  160. 


Fig.  161. 


Fig.  162. 


and  articulated,  the  screw  is  put  through  the  crown,  amalgam 
packed  in  the  crown-groove  and  around  the  screw,  which  is 
then  inserted  in  the  root,  and  the  crown  pressed  hard  into  its 
place.  The  screw  is  then  turned  into  the  position  shown  in 
Fig.  160,  thus  compressing  the  amalgam  or  cement  in  both 
recess  and  groove,  after  which  the  screw-head  may  be  covered 
with  amalgam,  cement,  or  gold,  as  desired. 

"  As  a  preferable  mode,  however,  the  screw-post  may  first  be 
fixed  in  the  root,  the  crown  adjusted  over  the  post,  amalgam 
packed  on  the  root  and  around  the  post,  the  crown  seated  firmly, 
more  amalgam  packed  in  the  crown  cavity  around  the  post,  and 
then  a  nut  screwed  on  the  post,  as  shown  in  Fig.  161.  In  all 
the  sectional  cuts  cement,  amalgam,  or  gutta-percha  is  to  be 
understood  as  filling  the  cavities  in  the  conjoined  roots  and 
crowns. 

"  Fig.  162  shows  in  contour  a  dovetailed  crown  mounted  on  a 


ROOT    CROWNING, 


215 


superior  molar  root  in  the  manner  shown  by  Fig.  155.  It  is 
obvious  that  the  crown  of  Fig.  155  might  be  ground  quite  down 
to  the  post-ends,  and  yet  be  firmly  held  by  the  dovetail  sides  of 
the  central  cavity." 

The  Gates  Crown. — The  Gates  crown  is  quite  similar  to  the 
Bonwill  crown.     It  is  usually  attached  to  the  root,  however,  by 


Fig.  163. 


a  metallic  screw  manufactured  for  the  purpose,  such  as  is  illus- 
trated in  Fig.  164,  instead  of  the   Bonwill  pin.     The  screw  is 
first  inserted  in   the   root   and  the  amalgam  packed 
around  it.     In  nearly  all  roots,  at  a  reasonable  dis-  "  ^^' 

tance  up  the  canal,  a  suitable  place  for  fastening  the 
end  of  the  screw  can  be  found.  Too  much  force 
must  not  be  applied  in  its  insertion,  as  a  root  is  easily 
split.  In  bicuspid  and  molar  crowns  nuts  are  used 
on  the  screws,  which  fit  slots  in  the  grinding-surface 
of  the  porcelain.  They  are  screwed  into  the  amalgam 
or  cement,  and  covered  with  it  in  the  process  of  cementation  of 
the  crown. 

The  Foster  'Crown. — The  Foster  crown  also  resembles  the 
Bonwill,  but  has  less  concavity  at  the  base.  The  crown  is 
attached  to  the  root  by  a  headed  screw  (Fig.  166)  or  a  screw 
with  a  nut,  instead  of  the  Bonwill  pin. 


2l6 


MECHANICAL    DENTISTRY. 


The  How  screws  and  instruments  (Fig  167)   are  best  adapted 
for  use  with  these  crowns. 

Fig.  165.  ^"^-  '6^- 


Fig.  168.        Fig.  169.        Fig.  170. 


1 


h 


The  Rowland  Crown. — This  crown  is  attached  like  the  How 
dovetail  crown,  with  screws  that  are  first  inserted  in  the  root. 
It  is   used  mostly  on  bicuspid  and  molar  roots,  and 
Fig.  167.     consists  of  a  hollow  porcelain  crown,  with  a  cavity  in 
i  the  crown   sufficiently  large  to  admit  the  screws  or 

i    ^         pins  (Fig.  168)  and,  when  necessary,  a  small  portion 
I    (\         of  the  root. 
J.  The    method    of    set- 

ting this  crown,  as  de- 
scribed by  Dr.  S.  E. 
Howland,  the  inventor, 
is  to  trim  the  root  even 
with  the  gum,  with  a 
stump  file  (a  corundum 
stone  or  the  Ottolengui 

root-facer  on  the  dental  engine,  however,  is  more 
suitable) ;  fit  the  crown  to  the  root ;  enlarge  the  root- 
canal  so  that  a  threaded  pin  of  proper  size  will  pass 
in  easily,  partially  fill  the  canal  with  zinc  phosphate, 
and  press  the  pin  to  its  place  with  pliers.  The  crown 
should  then  be  filled  with  zinc  phosphate  and  pressed  to  its 
place,  care  being  taken  to  hold  it  in  position  until  the  cement 
sets  (Fig.  169).  If  any  operator  distrust  the  ability  of  zinc 
phosphate  to  make  a  perfect  joint,  a  small  quantity  of  silver 
amalgam  or  gutta-percha  can  be  used  to  advantage. 

This  crown  is  strong,  and  during  its  test  of  several  years 
none  have  broken,  so  far  as  known.  The  mode  of  fastening  is 
strong  and  simple,  and  when  set,  if  a  good  joint  has  been 
made,  none  of  the  phosphate  or  other  setting  material  is  visible. 
It  is  a  perfect  imitation  of  the  natural  tooth  (Fig.  170). 


ROOT    CROWNING. 


217 


PORCELAIN    CROWNS    WITH    GOLD    COLLAR    ATTACHMENT. 

A  very  good  combination  for  some  cases,  is  to  use  a  gold 
collar,  either  seamless  or  soldered,  in  combination  with  any  of 
the  porcelain  crowns. 

The  root  having  been  properly  prepared  to  receive  a  collar,  it  is 
adjusted  and  adapted  the  same  as  for  the  Richmond  crown  (see 
page  224).     The  porcelain  crown,  the  base  of  which  should  be 
fully  as  large  as  the  end  of  the  root,  is  then  ground  even  with 
the  cervical  wails,  and  fitted  into  the  collar,  which  should  be 
trimmed  and  burnished  to  the  form  of  the  crown.     Dr.  Town- 
send's  fusible  metal  die,  used  in  the  following  manner,  facilitates 
the  application  of  a  collar  to  a  Logan  crown  (Fig.  171).     Prepare 
the  root-canal  to  receive  the  pin.     Grind  a  suit- 
able Logan  crown  to  fit,  and  articulate  it.     Con-  Fig.  171. 
struct  a  band  of  No.  30  gold  (for  instructions  see  /  \ 
page  226),  which  should  be  wide  enough  to  pro- 
ject beyond  the  end  of  the  root  ^^2  ^^  ^^  inch. 
Cut  a  wooden  peg  about  an  inch  long  and  taper 
one  end  of  it  to  the  general  size 


and  shape  of  the  pin  in  the 
Logan  crown.  Place  the  band 
on  the  root,  insert  the  peg  in 
the  canal,  and  fill  up  the  band 
with  Melotte's  moldine,  press- 
ing it  closely  about  the  peg. 
Remove  all  together  and,  holding  the  die  over 
the  flame  of  an  alcohol  lamp  to  melt  the  fusible 
metal,  place  them  altogether  on  the  die,  with  the 
pin  in  the  socket,  and  press  down  until  the 
moldine  rests  on  the  surface  of  the  molten  metal. 
Then  carefully  chill  the  tooth  ;  in  cooling,  the 
fusible  metal  takes  a  firm  hold  on  the  lower  edge  of  the  gold 
band,  holding  it  securely  in  place  during  the  remainder  of  the 
operation.  Now  remove  the  peg  and  the  moldine,  and  with  a 
wooden  mallet  drive  the  Logan  crown  into  the  band  i//i^i/  tlie 
porcelain  rests  Jipon  the  fusible  metal.  Burnish  the  band 
smoothly  about  the  crown.     When  it  is  perfectly  adjusted  to 


I.  Socket.    2.  Fusible 
Metal. 


2l8 


MECHANICAL    DENTISTRY. 


the  porcelain,  melt  the  fusible  metal  to  release  the  band  and 
crown. 

If  the  work  has  been  carefully  done,  the  crown  will  then  be 
ready  to  be  adjusted  in  the  mouth. 

Enough  of  the  labial  portion  of  the  band  should  be  trimmed 


Fig.  172. 


Fig.  173. 


Fig.  174. 


away  to  prevent  too  conspicuous  exposure  of  the  gold  (Fig. 
172). 

This  collar  combination  is  available  in  very  difficult  cases,  as, 
for  instance,  when  a  root  is  decayed  upon  one  side  beneath  the 
gum  margin,  as  seen  in  Fig.  173. 

This    operation,  when    completed,  would    appear    in  vertical 


Fig.  175. 


Fig.   176. 


Fig.  177. 


section  like  Fig.  174,  and  a  view  in  perspective  would  resemble 

Fig.  175- 

Dr.  E.  C.  Kirk's  Method,  of  combining  the  porcelain  crowns 
with  a  band  or  collar,  is  shown  in  Figs.  176  and  177.  Here  the 
Foster  crown  is  employed.  First  a  collar  is  made  and  fitted  to 
the  root ;  it  is  cut  narrow  on  the  labial  side,  and  left  wide  on  the 


ROOT    CROWNING.  2I9 

lingual,  so  that  it  shall  extend  nearly  to  the  cusp  of  the  crown 
when  finished  (Fig.  177).  The  seamless  gold  collars  are  well_ 
suited  for  application  to  this  style  of  crown. 

The  crown  selected  should  have  a  somewhat  greater  circum- 
ference at  the  base  than  the  collar,  so  that  when  ground  down 
somewhat  conically  on  its  lingual  and  approximal  surfaces,  it 
can  be  tightly  adjusted  to  the  collar,  which  would  be  impossible, 
if  a  crown  smaller  than  the  collar  is  used.  The  screw  is  fitted 
so  that  it  will  hold  the  crown  in  proper  relations  with  the  root. 
It  is  then  removed  with  the  crown,  the  parts  dried,  and  the  root- 
canal  filled  with  a  slow-setting  oxyphosphate  cement.  The 
crown  is  then  pressed  home,  the  surplus  cement  flowing  through 
the  opening  in.  the  porcelain  and  filling  up  any  interstices 
around  or  between  the  band,  the  root,  and  the  crown.  The 
screw  is  then  forced  to  position,  and  when  the  cement  is 
set  perfectly  hard  the  head  of  the  screw  or  the  nut  on  it  is 
notched  to  form  a  retaining-pit,  and  the  countersink  of  the 
crown  filled  with  gold. 

Dr.  C.  S.  W.  Baldwin's  Method  is  to  cap  the  root  and  at- 
tach a  Logan  crown  m  the  following  manner : — 

First,  the  root  is  shaped  for  the  proper  adaptation  of  the 
band.  The  band  and  cap  are  then  made  as  directed  for  the 
Richmond  crown  on  page  226.  The  edges  are  then  trimmed 
to  fit  the  festoon  of  the  gum ;  a  hole  drilled  from  the  inner  side 
for  the  pin,  leaving  the  raggedness  made  by  drilling  to  catch  in 
the  cement.  Place  the  cap  on  the  root  and  fit  the  porcelain 
crown  accurately  to  it  in  the  desired  occlusion  and  position. 
Fig.  178  shows  a  root,  cap,  and  a  Logan  crown.  A  crown 
having  the  H-shaped  pin,  but  square  on  the  edge,  like  some  of 
the  early  patterns  of  Logan  or  Bonwill  crowns,  would  reduce 
the  time  of  setting  and  give  best  results.  Having  polished  the 
edges  of  the  cap,  the  crown  may  be  conveniently  adjusted  as 
follows  :  Place  oxyphosphate  cement  in  the  countersunk  portion 
of  the  porcelain,  and  in  the  canal  only  enough  cement,  of 
creamy  consistency,  to  nil  it,  as  the  pressure  required  to  force 
out  the  surplus  under  the  edges  of  the  cap  destroys  many  nicely 
adjusted  crowns,  leaving  bulging  irritants  instead  of  smooth 
supports.     If   proper    attention   has  been   given  to    fitting   the 


2  20 


MECHANICAL    DENTISTRY. 


crown  and  root,  all  will  come  nicely  to  place ;  but  in  some  cases 
of  difficult  adjustment  it  may  be  necessary  to  cement  the  crown 
to  the  cap  before  fastening  the  pin  in  the  root  (Fig.  179). 

In  most  cases  the  gold  band  will  be  invisible  and  below  the 
free  margin  of  the  gum.  There  are  instances,  where  the  anterior 
teeth  are  prominent,  that  it  will  be  necessary  to  cut  away  the  top 
of  the  cap  in  front,  allowing  the  porcelain  to  come  directly  in 
contact  with  the  root,  the  band  going  deeper  than  in  ordinary 
cases,  which  prevents  the  appearance  of  gold  (Fig.  180). 

Dr.  Bonwill's  plan  is  to  cap  the  tooth  with  a  platinum  or  gold 
cap  having  a  slot,  into  which  the  pin  passes  as  it  is  slipped  on 
the  root  (Fig.  181).  The  crown  is  then  secured  with  amalgam 
in  the  usual  way. 


Fig.  178. 


Fig.  179. 


Fig.  180. 


Fig.  181. 


Dr.  Sidney  S.  Stowell's  Method  is  as  follows:  Make  a 
closed  cap,  using  the  combination  crown  metal,  and  place  it 
upon  the  root.  The  cap  is  then  perforated  and  the  root  reamed 
for  the  dowels.  The  bite  in  wax  is  now  taken,  after  which  the 
cap  is  burnished  into  the  countersunk  end  of  the  root  (Fig.  183). 
The  dowels  of  platinum  and  iridium  wire  are  now  set  in  their 
places,  being  allowed  to  project  one-fourth  of  an  inch  so  that 
they  may  adhere  to  the  impression  of  plaster  which  is  then  taken. 
From  this  a  cast  is  made  of  investing  material ;  calcined 
marble-dust  and  plaster  is  preferable,  though  fine  molding-sand 
will  do.  The  dowels  are  now  cut  off  even  with  the  top  of  the 
cap  (Fig.  184). 


ROOT    CROWNING. 


22  I 


The  tooth  to  be  used  may  be  a  Logan  or  Brown  crown,  or  a 
common  countersunk  tooth,  but  I  would  in  most  cases  recom- 
mend the  Logan  crown.  As  the  case  in  question  is  a  bicus- 
pid, I  have  selected  for  it  a  Logan  crown.  First,  cut  off  the 
pin,  and  then  the  tooth  is  ground  into  position  on  the  cap ; 
grinding  the  stump  of  the  pin  and  porcelain  alike  evenly  and 
smoothly.  The  stump  of  the  pin  is  now  ground  with  a  small 
wheel  below  the  surface  of  the  porcelain  (Fig.  185).  The  tooth 
is  invested  (Fig.  186),  and  pure  gold  fused  on  to  the  platinum 
pin,  and  while  in  a  fluid  state  it  is  with  a  wax  spatula  spatted 
down  flat  (Fig.  187).  The  gold  is  filed  or  ground  down  even 
with  the  porcelain,  and  at  the  palatal  border  the  tooth  is  ground 
to  bevel  back  until  the  gold  is  reached  (Fig.  188).  The  tooth 
is  now  fastened  in  place  on  the  cap  with  wax  cement  (Fig.  189), 

Fig.  182.  Fig.  1S3.  Fig.  1S4.  Fig.  185.     Fig.  186.    Fig.  187.    Fig.  1S8.  Fig.  189. 


the  cast  cut  away,  and  the  case  invested  in  asbestos  and  plaster 
(Fig.  190).  This  is  used  because  of  the  fiber  of  the  asbestos, 
which  prevents  the  separation  of  the  crown  and  cap.  The  wax 
is  removed  with  boiling  water,  or  is  burned  out,  the  case 
thoroughly  heated  up,  then  a  small  clipping  of  thin  platinum 
plate  is  crowded  into  the  opening  (see  Fig.  190)  caused  by  the 
grinding  of  the  bevel  on  the  crown.  The  clipping  of  platinum 
serves  as  a  lead  for  the  solder,  which  follows  it  down  into  the 
countersunk  cap,  around  the  ends  of  the  dowels,  and  finally 
attaches  itself  to  the  pure  gold  already  firmly  attached  to  the 
stump  of  the  platinum  pin.  When  cool  the  case  is  removed 
from  the  investment,  dressed  and  polished  (Fig.  191).  A  sec- 
tional view  of  a  like  tooth  (Fig.  192)  shows  the  organization  in 
detail. 

Fig.  193  shows  a  central  incisor  root  on  which  a  Logan  crown 
is  used  after  this  method.     Fig.  194  shows  how  delicately  an 


222 


MECHANICAL    DENTISTRY. 


operation  of  this  kind  may  be  performed  upon  an  inferior  central 
incisor,  by  the  use  of  the  countersunk  tooth-crown,  which  is 
shown  as  it  appears  before  gold  has  been  melted  in  its  cup 
around  the  pin;  when  the  cup  has  been  filled  with  gold,  and 
after  the  crown  has  been  ground  and  beveled.  A  countersunk 
molar  crown  is  shown  as  likewise  mounted  on  the  roots  of  a 
superior  left  second  molar  (Fig.  195). 

The  cuts  are  made  from  photographs  of  prepared  specimens, 
the  natural  roots  of  which  vary  in  the  several  figures;  and  in 
the  section  (Fig.  192)  the  continuation  of  the  pulp-canal  does 
not  appear,  because  obliterated  in  preparing  the  section. 

The  claims  for  this  method  of  crown-work  are  as  follows  : 
The  combination  of  an  all-porcelain  crown  with  a  closed  cap  and 


Fig.  190. 


Fig.  191.       Fig.  192.       Fig.  193.         Fig.  194. 


mj^t 


~^y 


Fig.  191;. 


dowels;  the  adaptation   of  which  crown  and  its  final  attachment 
to  the  root  can  be  made  perfect. 

The  dowels  may  be  set  at  any  angle  that  the  direction  of  the 
root-canal  may  indicate,  using  one  or  more  dowels  as  the  case 
may  require,  and  when  the  root  has  to  be  cut  off  much  below 
the  gum,  and  a  collar  cannot  be  placed,  a  platinum  disk-floor  on 
the  root-end  is  the  preferable  plan.  The  well  known  and  easily 
detected  plate-tooth  having  a  gold  backing  which  renders  the 
tooth  dull  in  appearance  is  thus  made  obsolete,  for  this  crown 
possesses  the  translucent  appearance  of  the  natural  organ.  Best 
of  all,  the  glaring  gold  of  which  some  so-called  beautiful  crowns 
are  almost  entirely  composed  is  by  this  means  superseded.  We 
here  refer  to  gold  bicuspids  and  molars,  more  especially  to  the 
former;  it  was  the  unsightly  appearance  of  these  which  first  led 
us  to  try  and  improve  on  them.) 


ROOT    CROWNING. 


223 


While  recognizing  the  unquestioned  value  of  the  closed  cap 
and  dowel,  I  respectfully  present  a  supplemental  method  which 
results  in  a  crown  possessing  all  the  merits  of  the  former  with 
additional  embodiment  of  strength,  beauty,  and  practicability. 

Dr.  Shulze's  Method. — Another  method  of  crowning,  by 
using  a  plain  rubber  porcelain  tooth  in  combination  with  a  gold 
collar  is  that  described  by  Dr.  Wm.  H.  Shulze,  Atchison,  Kansas. 
The  doctor  says  :  My  mode  of  utilizing  the  plain  rubber  porcelain 
tooth  for  a  bicuspid  crown  will  be  found  to  be  both  simple  and 
practical.  After  preparing  a  tooth-root  as  for  an  all-gold  crown 
by  fitting  over  the  root-neck  a  gold  collar  of  the  proper  width,  as 
in  Fig.  196,  remove  and  cut  away  the  front  of  the  collar  (Fig. 
197).  Bevel  the  labial  edge  of  the  root  so  that  the  tooth  can  set 
well  into  the  collar  (Fig.  198).     Replace  the  collar  on  the  root, 

Fig.  196.  Fig.  197.  Fig.  198.  Fig.  199.    Fig.  200.    Fig.  201.    Fig.  202.      Fig.  203. 


dry  out,  and  place  a  little  softened  wax  on  the  end  of  the  root. 
Select  a  suitable  plain  rubber  tooth,  nip  off  the  heads  of  the  pins, 
grind  so  that  it  will  enter  the  collar,  adjust,  and  articulate,  press- 
ing the  tooth  against  the  wax.  Carefully  remove  the  collar  and 
tooth  (Fig.  199).  Invest  in  plaster  and  asbestos  fiber  (Fig.  200), 
Fit  a  thin  piece  of  platinum  into  the  collar,  burnishing  it  down 
on  the  tooth,  and  bending  it  down  to  the  pins.  If  it  is  de- 
sired to  use  a  post,  remove  and  punch  the  platinum  plate  at  the 
proper  place,  and  solder  in  a  post;  replace  within  the  collar, 
and  secure  with  a  piece  of  binding-wire  imbedded  in  the  invest- 
ment (Fig.  200).  A  little  18  k.  solder  will  join  together  the  collar, 
platinum  plate,  and  tooth-pins  (Fig.  201).  If  there  are  any 
places  where  the  collar  does  not  fit  the  tooth  closely,  pack  in 
gold  foil  before  soldering.  If  the  inner  cusp  does  not  fill  the 
collar,  or  it  needs  lengthening  for  occluding  purposes,  get  the 
desired   shape   with   wax  when  fitting  the  tooth.     Remove  the 


224  MECHANICAL    DENTISTRY. 

wax  after  investment,  pack  in  gold  foil  pellets,  and  add  enough 
20  k.  solder  to  flow  through  it,  and  the  desired  addition  will  ap- 
pear as  in  Fig.  202.  The  completed  crown,  mounted  as  usual 
with  cement,  is  shown  in  Fig.  203. 

The  advantages  of  this  method  are  its  simplicity,  ease  of 
adaptation  and  articulation,  the  short  time  required  to  fit  and 
make  the  crown,  its  strength,  security,  and  natural  appearance, 
and  the  convenience  of  using  a  plain  rubber  or  saddle-back 
tooth. 

FERRULE  OR  COLLAR  CROWNS. 

The  Richmond  Crown. — This  crown  was  originally  brought 
to  the  notice  of  the  profession  by  Dr.  C.  M.  Richmond,  of  New 
York.  Numerous  modifications  have  been  made,  however, 
which  enhance  its  value.  The  process  of  constructing  the  im- 
proved crown  is  as  follows  : — 

I.  The  root  must  be  trimmed  down  to  about  the  gum-line,  ex- 
cept the  labial  portion,  which  should  be  cut  nearly  a  sixteenth  of 
an  inch  below  the  gum  margin.    For  this  purpose, 

Fig.  204.  corundum  stones  or  the  Ottolengui  root-facers 

i~^^  f^^      are  employed,  as  shown  in  the  preparation  of  roots 
I       f  f~~l      ^'^  ^'^^  Logan  Crown.     (See  pages  190,  192.) 
I   ,  I    I      M  2.  The  ring  of  enamel  remaining  upon  the  root 

\  /  I  w  should  be  carefully  and  thoroughly  removed, 
^  iM  (see  Fig.  204)  making  the  sides  of  the  root 
parallel,  so  that  the  band,  when  applied  may  fit 
closely  its  entire  zvidth.  If  this  is  not  done,  the  band,  even  if 
a  narrow  one,  instead  of  fitting  closely  will  form  a  pocket 
beneath  the  gum  margin,  and  will,  in  consequence  of  its  irri- 
tating effect  upon  the  surrounding  tissues,  cause  more  or  less 
inflammation  and  possibly  the  loss  of  the  root. 

Numerous  instruments  have  been  devised  for  the  removal  of 
this  enamel ;  among  the  most  efficient  are  those  invented  by 
Dr.  Calvin  S.  Case  and  Dr.  Geo.  M.  Weirich.  Fig.  205  illus- 
trates Dr.  Case's  enamel  cleavers.  These  are  so  shaped  that 
they  can  be  partially  rotated  under  the  margin  of  the  gum, 
presenting  a  sharp  point  toward  portions  of  the  enamel  that  will 
not  easily  clean  ofl",  with  a  view  to  fracturing  it  as  the  diamond 
cuts  glass,  breaking  it   up  into  small  pieces  which  can  readily 


ROOT    CROWNING. 


22  = 


be  detached  and  the  sides  straightened  and  smoothed  by  the 
Fig.  205.  Fig.  206. 


IS   V 


broad  blade.  The  pecuHari- 
ties  of  shape  are  shown  in 
the  enlarged  cuts. 

The  Weirich  cleaver  or 
chisel  is  shown  in  Fig.  206. 
With  this  instrument  and  a 
few  gentle  blows  from  the 
mallet  the  enamel  is  readily  broken  up  and  de- 
tached. The  rubber  cushion  in  the  center  of  the 
chisel  takes  up  the  blow,  thus  relieving  the  root 
from  unnecessary  shock.  In  the  accompanying 
illustration  the  instrument  is  shown  in  place  ready 
to  receive  the  blow  from  the  mallet.  It  is  a  well- 
known  fact  that  with  most  of  the  appliances  on  sale 
it  is  difficult  to  properly  remove  the  enamel  from 
the  approximal  surfaces  of  roots,  especially  where 
they  are  very  close.  With  this  instrument  (to  be 
followed  with  the  ordinary  cervical-wall  chisel  or 
the  Chase  cleavers)  the  root  upon  all  sides  can  be 
readily  and  properly  prepared  for  the  reception  of 
a  band  or  collar  with  very  little  discomfort  to  the  patient 
or  trouble  to  the  operator. 

3.  After  the  enamel  has  been  thoroughly  removed,  an 
accurate  measurement  of  the  neck  of  the  root  should 
be  secured.  For  this  purpose  Dr.  A.  I.  F.  Buxbaum,  of 
Cincinnati,  has  devised  an  instrument  known  as  Bux- 
baum's  dentimeter,  with  which  the  work  can  be  very 
satisfactorily  performed.  It  is  illustrated  in  Fig.  207.  It 
ery  simple  to  adjust  and   operate,  and  has    the    advantage 


226 


MKCHANICAL    DENTISTRY. 


over  other  instruments  of  this  kind,  that,  as  you  do  not  have 
to  twist  the  entire  instrument,  the  wire  does  not  incline  to  sh'p 
off  the  root  or  lacerate  the  gum. 

Dr.  Buxbaum  gives  instructions  for  using  his  dentimeter  as 
follows  :  Pass  one  end  of  a  soft  wire  through  tube  at  C,  as 
shown  in  Fig.  2  of  accompanying  illustration,  and  wrap  once 
around  knob  D.  Pass  the  other  end  of  wire  through  tube  at  E, 
as  shown  in  Fig.  2,  and  wrap  around  knob  F.  Place  the  loop 
H  around  the  tooth  or  root.  While  unscrewing  the  screw, 
by  holding  milled  nut  B  between  the  thumb  and  forefinger  of 

Fig.  207. 


right  hand,  you  must  make  constant  traction  on  loop  around  the 
tooth  by  gently  pulling  on  barrel  A,  held  between  thumb  and 
finger  of  left  hand,  this  will  give  a  perfect  twist,  as  shown  in 
3.  Unfasten  ends  of  wire  from  the  knobs  D  and  F  and 
thdraw  from  dentimeter.  The  result  is  shown  in  Fig.  4. 
)ther  and  simpler  instruments  for  taking  measurements  of 
fehil*/  roots  have  been  devised,  notably  the  one  by  Dr.  Geo. 
^eirich,  of  Philadelphia,  which  is  shown  in  Fig.  208. 
'\4.  ■  §1  order  to  transfer  this  measurement  accurately  to  theband- 
m^^ffl^terial,  cut  the  wire  loop  in  the  center  and  spread  the  ends 
in  "^posite  directions,  as  shown  in  Fig.  209.  It  is  then  laid 
on  the  piece  of  gold  to  be  used  for  the  band  (which  should  be 
22  k.  and  about  30  gauge) ;  this  should  be  cut  the  exact  length 
of  the  zuire,  and  about  an  eighth  of  an  inch  in  width,  unless  for 


ROOT    CROWNING. 


227 


special  reasons  it  is  necessary  to  have  it  wider, 
of   gold    should 


This  small  strip 


now  be  annealed 
over  a  lamp   or 


Fig.  208. 


A 


Fig.  209. 


Bunsen    burner, 
then  with  round- 
nosed    pliers    it 
should        be 
brought    into    a 
circular     form, 
and  with  the  fin- 
gers    the     ends 
should  be   care- 
fully pressed  by  each  other.     This  will  form  a  slight 
kink  in  the  band,  so  that  the  ends,  if  now  gently  drawn 
apart  and  let  go,  will  spring  accurately  together  ready 
for  soldering. 

5.  In  soldering  the  band,  a  corner  of  the  two  edges 

should  be  grasped  with  the  soldering 
pliers,  the  joint  should  be  slightly  coated 
with  borax,  and  a  small  piece  of  20  k. 
solder  placed  over  it,  07i  the  outside  of  the 
band  (see  Fig.  210).  It  should  then  be 
held  in  the  flame  of  a  Bunsen  burner  until 
the  solder  flows,  at  which  time  it  should 
be  instantly  removed.  With  a  little  ex- 
perience and  care  in  soldering  in  this  way 
(over  a  Bunsen  burner),  it  can  be  done 
more  conveniently,  in  less  time,  and  with  much  less 
danger  of  burning  the  band,  than  with  the  blowpipe. 

6.  The  band  is  now  ready  to  be  fitted  or  adjusted  to 
the  root.  If  the  end  of  the  root  is  not  round,  as  is 
usually  the  case,  the  sides  of  the  band  can  be  flattened 
or  otherwise  shaped  with  slight  pressure  from  the  thumb 
and  finger  or  with  suitable  pliers.  The  upper  border  should 
then  be  trimmed  to  conform  to  the  shape  of  the  process  or  the 
line  of  the  gum-attachment ;  in  many  cases,  unless  the  band  is 
greatly  depressed  or  cut  out  on  the  sides,  it  will  be  found  that 


228 


MECHANICAL    DENTISTRY, 


the  gum  will  be  detached  from  the  sides  of  the  root,  and  that 
the  process  will  be  reached  before  the  root  is  covered  high 
enough  on  the  labial  and  palatal  surfaces.  Place  the  band  thus 
shaped  upon  the  root,  and  if  the  measurement  and  each  pro- 
gressive stage  have  been  accurately  performed,  it  will  be  found 
to  fit  perfectly.  Now  press  or  drive  it  up  carefully,  until  the 
point  of  attachment  between  the  soft  tissues  and  the  root  are 

Fin.  2IO. 


reached  (about  one-sixteenth  of  an  inch  beyond  the  gum  margin), 
which  is  shown  by  the  slight  whitening  of  the  gum.  When  this 
is  very  marked  upon  any  side,  the  band  should  be  removed 
and  relieved  by  cutting  it  away  at  that  point,  and  then  read- 
justed. A  corundum-wheel  is  now  gently  passed  over  the  labial 
portion  of  the  lower  edge  of  the  band,  to  level  it  with  the  face 
of  the  root  and  to  render  the  band  invisible  when  the  crown  is 
finished.  In  doing  this  the  wheel  used  should  be  revolved  toivard 
the  root,  so  it  will  not  irritate  the  soft  tissues,  as  it  would  were 
the  force  applied  in  the  opposite  direction, — and  at  the  same  time 
it  will  turn  the  feather-edge  of  metal  over  the  end  of  the  root. 
7.  The  base  plate  is  more  easily  and  quickly  formed.  Cut  a 
piece  of  gold  (32  to  34  gauge)  of  suitable  length  and  width, 
anneal,  and  then  press  it  against  the  lower  edge  of 
the  band  with  the  fingers  until  it  is  nicely  adapted  ; 
secure  it  in  this  position  for  soldering  by  three  or 
four  strands  of  wire,  as  shown  in  Fig.  211.  Now 
paint  the  joint  with  borax  dissolved  in  water,  lay  a 
small  piece  of  20  k.  solder  against  the  back  or  palatal  portion 
of  the  band,  011  the  outside,  and  hold  it  in  the  flame  of  a  Bunsen 
burner  until  the  solder  flows,  which  will  be  seen  to  run  entirely 
around  the  band,  uniting  it  with  the  base  plate  at  every  point. 
The  surplus  of  the  base  plate  material  should,  with  shears  and 
corundum  stone,  be  trimmed  off  flush  with  the  band,  the  two 
now  forming  a  complete  cap  for  the  face  and  sides  of  the  root. 


Fig.  211. 


ROOT    CROWNING.  229 

8.  The  next  step  is  the  preparation  and  adjustment  of  a  pin 
through  the  cap  into  the  root  canal.  The  canal  should  be  en- 
larged toward  the  palatal  side  of  the  root ;  this  will  give  more 
room  when  we  come  to  grind  the  tooth,  and  at  the  same  time 
secure  the  greatest  attainable  strength  when  the  crown  is  com- 
pleted. 

The  base  plate  of  the  cap  is  perforated  at  a  point  directly  over 
the  opening  into  the  canal.  This  may  be  done  either  with  a 
bur  on  the  dental  engine  or  with  the  plate  punch.  A  pin  of 
platinum  wire,  number  16  or  17,  standard  gauge,  should  now 
be  slightly  tapered  at  the  end  and  passed  through  the  aperture 
made  in  the  cap  and  up  into  the  root  canal.  The  end  of  the 
pin  projecting  below  the  cap  may  be  marked,  withdrawn,  and 
bent  at  a  right  angle,  so  that  it  will  point  away  from  the  tooth, 
that  is,  toward  the  palatal  surface;  it  may  then  be  waxed  in, 
invested,  and  soldered  with  the  tooth,  or,  invested  and  soldered 
at  this  stage,  and  the  surplus  of  pin  and  solder  brought  down 
flush  with  a  file  or  stone. 

9.  The  cap  and  pin  should  be  readjusted  to  the  root.  A  plain- 
plate  tooth,*  of  suitable  form  and  color,  is  now  ground  and  fitted 
to  the  cap.  The  labio-cervical  edge  of  the  tooth  («,  Fig.  212), 
should  be  so  ground  that  it  will  be  flush  with  the  edge 

of  the    band   and   meet   the   margin  of  the  gum.      It   ^'^'  ^^^' 
should  also    be  ground  out  at  the  center  of  the  base 
{p),  so  as  to  form  a  slight  space  just  over  the  base  of 
the  pin. 

The  tooth  is  then  backed  with  either  thin  platinum 
or  gold-plate  (gold  will  give  a  slight  yellow  shade  to 
the  tooth  while  platinum  will  give  a  bluish  tint).     The  upper 
edge  of  the  backing,  brought  down  thin  with   a  file  or  stone, 
should  extend  as  far  as  possible  under  and  between  the  tooth 


*  Many  writers  advise  using  cross-pin  teeth  ;  it  is  self-evident,  however,  that  in  this 
work  straight-pin  teeth  should  be  employed  and  the  cross-pins  avoided  wherever  pos- 
sible, for  the  following  reasons  :  (i)  The  position  of  the  pins  weakens  the  body  of 
the  tooth.  (2)  Their  position  makes  the  strain  upon  the  tooth  greater,  as  it  gives  in- 
creased leverage  between  the  pins  and  the  cutting  edge.  (3)  There  is  more  liability 
of  cracking  the  teeth  in  soldering,  on  account  of  so  much  metal  being  brought  at  one 
point. 


230  MECHANICAL    DENTISTRY. 

and  the  cap,  so  that  the  solder  will  more  readily  flow  in  and  fill 
what  space  there  may'  be.  The  incisive  edge  of  the  backing 
should  also  be  brought  slightly  over  the  edge  of  the  porcelain 
(though  it  is  not  so  shown  in  the  accompanying  illustrations), 
this  portion  of  the  tooth  being  previously  beveled  with  a  fine 
corundum  stone.  In  this,  the  possibility  of  breaking  the  tooth 
from  the  force  of  mastication  is  much  diminished. 

10.  A  perfect  joint  and  the  proper  length  and  angle  of  the 
tooth  having  been  secured,  the  pieces,  that  is,  the  tooth,  cap,  and 
pin,  should  now  be  thoroughly  dried  and  then  held  together  in 
the  proper  relationship,  and  secured  in  this  position  by  running 
warm  adhesive  (resin)  wax  over  the  palatal  portion  of  the 
tooth,  attaching  the  backing  to  the  cap.  It  should  then,  before 
the  wax  gets  very  hard,  be  carefully  carried  to  position  upon  the 
root,  when  any  correction  in  the  position  of  the  tooth  can  readily 
be  made.  Now  apply  a  little  cold  water  from  the  syringe  or  on 
a  pledget  of  cotton  ;  this  will  harden  the  wax,  so  that  the  crown 
may  be  removed  without  changing  the  position  of  the  tooth 
upon  the  cap.  It  will  then  be  ready  to  be  invested  for  soldering. 
A  most  suitable  investment  for  crown  work  is  marble-dust 
and  plaster,  equal  parts,  with  a  small  quantity  of  fine  asbestos 
fiber  thoroughly  incorporated.  After  the  investment  has  thor- 
oughly set,  the  wax  may  be  removed  and  the  surface  of  the 
backing  and  cap  cleansed  by  directing  upon  it  a  small  stream 
of  boiling  water.  The  investment  should  be  cut  away  so  as  to 
expose  the  sides  of  the  backing  and  the  lower  border  of  the 

band,  as  illustrated  in   Fig.  213,  but  every 

-.        ^  portion    of   the    porcelain    should    be    pro- 

^,_^^^.    ^^  tected.     The  case   should  then  be   at   first 

/^      \hif^.''      >^       gently  heated  up,  to  drive  off  the  moisture, 

I       :      /  A      then  transferred  to  the  soldering  block,  when, 

l^  p     with   the   blowpipe,   more   heat    should    be 

applied,  continuously  at  first,  until  the  in- 
vestment and  tooth  are  thoroughly  and  evenly  heated  through- 
out. Gold  solder,  18  k.,  is  then  cut  in  small  pieces  and  placed, 
with  a  little  borax,  over  the  aperture  between  the  backing  of 
the  tooth  and  the  cap.  The  investment  being  now  uniformly 
heated,  the  flame  from  the  blowpipe  should  be  directed  upon  the 


ROOT    CROWNING.  23  I 

solder,  mostly  in  the  direction  indicated  in  Fis;.  213,  when,  if 
the  entire  case  has  been  previously  brought  to  a  red  heat,  the 
solder  will  readily  melt  and  flow  between  the  tooth  and  cap. 
Additional  solder  should  now  be  added  and  melted  until  the 
proper  contour  of  the  tooth  is  insured. 

The  tooth  and  investment  should  then  be  placed  in  and  covered 
with  sand,  plaster,  or  some  other  suitable  substance  to  keep  the 
heat  from  radiating  too  rapidly  and  thus  cracking  the  tooth.  It 
should  be  left  so  covered  until  it  is  thoroughly  cool.  We  might 
add  here,  that  it  is  well  to  direct  the  flame  from  the  blowpipe 
into  the  sand  or  other  material  for  a  moment  before  placing  the 
tooth  in.  After  the  tooth  is  thoroughly  cool,  the  investment 
may  be  broken  away,  and  all  oxidation  and  borax  removed  by 
placing  it  for  a  few  minutes  in  the  acid  bath.  The  ^^^  ^ 
crown  is  then  ready  to  be  finished  and  polished.  The 
shaping  of  the  solder  can  best  be  done  with  corundum 
stones,  followed  with  hard-rubber  disks,  and  then  fine 
sand-paper  or  cuttlefish  disks,  while  the  polishing  is 
accomplished  with  brush  and  buff-wheels,  pumice 
stone,  whiting,  and  rouge.  The  completed  crown  in 
position  is  shown  in- Fig.  214. 

The  Richmond  Method  Applied  to  Bicuspid  Roots. — The 
capping  of  the  root  is  similar  to  that  already  described  ;  the 
crown  will  have  greater  strength,  however,  if  a  portion  of  the 
palatal  section  of  the  natural  crown,  when  strong  enough,  is 
retained,  and  the  band  made  deep  enough  to  cov^er  it.  One 
pin  is  all  that  is  usually  required,  and  where  there  are  two 
distinct  canals,  the  palatal  should  be  used  to  recei\-e  the  pin  ; 
thus  greater  strength  is  secured  at  the  point  where  it  is 
most  needed,  and  the  pin  is  so  located  that  it  will  not  inter- 
fere with  the  grinding  and  adjusting  of  the  tooth.  The  cap 
and  pin  being  in  position,  a  suitable  cuspid  tooth  or  bicuspid 
facing  is  then  ground,  backed,  and  adjusted  to  represent  the 
labial  aspect,  and  then  properly  secured  to  the  cap  with  adhe- 
sive wax.  The  tooth,  cap,  and  pin  are  then  carefully  removed, 
invested,  and  soldered;  after  which  the}"  are  again  placed  upon 
the  root,  and  the  occluding  edge  of  the  tooth  is  ground  clear  of 
the  antagonizing  teeth  at  about  the  angle  shown  at  A,  Fig.  21  ^. 


232 


MECHANICAL    DENTISTRY. 


Fig.  215. 


Fig.  216. 


From  a  suitable  die  or  die-plate  (see  page  180,  ctscq.)  the  cusps 
or  occluding  surface  of  the  tooth  is  swaged  from  22  k.  gold  plate. 
These  cusps  should  then  be  filled  in  with  18  or  20  k. 
plate  or  solder.  This  is  done  by  cutting  the  gold  into 
small  pieces,  and  placing  them,  with  a  little  borax,  in 
the  depressions  of  the  cusps,  all  of  which  is  held  over 
a  Bunsen  burner  until  the  small  pieces  are  melted, 
when  they  will  flow  into  these  depressions  and  fill 
them  level  full.  The  surplus  is  trimmed  away,  the 
cusps  ground  and  fitted  to  the  edge  of  the  porcelain 
front,  in  position  to  secure  proper  occlusion  (Fig.  216), 
and  secured  with  wax  as  shown  at  A. 

A  piece  of  thin,  pure  gold  plate  or  mica  is  then 
adjusted  on  each  side  of  the  crown  (B,  Fig.  216), 
the  surfaces  of  which,  if  dry  and  slightly  warm,  will 
be  held  in  position  temporarily  by  pressing  them 
gently  against  the  side  of  the  wax.  This  is  all  now 
invested  together  (Fig.  217). 

The  long  ends  of  these  side  pieces,  after  being  invested,  hold 
them  in  position,  as  the  investment  should  be  cut  away  so  as  to 
expose  the  sides  of  the  crown  as  shown  at  A,  Fig.  217.  In  the 
process  of  soldering,  after  the  case  has 
been  properly  heated,  the  small  pieces 
of  solder  and  borax  are  placed  in  the 
aperture  formed  by  these  sides  of  gold 
or  mica  (the  place  formerly  filled  with 
wax),  and  the  flame  from  the  blowpipe 
directed  cautiously  against  these  exposed 
sides  (A).  The  solder  will  then  flow, 
uniting  the  several  parts,  when  more  should  be  added  until  the 
proper  contour  with  perfect  continuity  of  structure  is  secured. 
The  crown  can  be  made  without  the  gold  or  mica  sides  if  great 
care  is  exercised  in  flowing  the  solder.  There  will  be  more 
surplus  solder,  however,  to  be  finished  off. 

In  finishing,  the  solder  is  brought  to  the  contour  of  a  bicuspid 
tooth  with  corundum  stones  and  sand-paper  disks,  when  it  is 
ready  for  the  polishing  process.  The  finished  crown  is  repre- 
sented in  place  upon  the  root  in  Fig.  218. 


Fig.  217. 


I- 


% 


ROOT    CROWNING.  233 

There  are  other  methods  practised,  and  though  some  of  them 
may  not  be  as  artistic  as  the  one  just  described,  they  are  much 
simpler  and  quicker.  For  instance,  the  palatal  cusp  „  „ 
may  be  built  up  with  several  pieces  of  gold  plate — 
previously  melted  into  the  form  of  balls  and  flattened 
out  with  a  hammer.  The  backing  is  brought  down 
and  closely  burnished  over  the  cutting  edge  of  the 
tooth,  which  is  then  waxed  in  position,  tried  in  the 
mouth,  and  invested,  and  when  ready  to  be  soldered, 
these  flattened  pieces  of  gold  are  laid  in  position, 
united  and  filled  in  with  18  k.  solder,  which  is  also  brought 
over  the  backing  to  the  tip  of  the  tooth.  This  plate  and  solder 
are  afterwards  brought  to  the  proper  shape  and  contour  with 
the  stones  and  disks. 

Then,  again,  the  palatal  portion  of  the  band  is  extended  down 
so  as  to  nearly  touch  the  antagonizing  tooth.  This  leaves  only 
a  comparatively  small  space  to  be  filled  in  with  solder,  which 
is  afterwards  trimmed  and  finished  to  the  form  of  the  crown. 

Or,  a  method  that  the  writer  often  employs,  is  to  back  the 
tooth,  grind  off  or  bevel  the  occluding  surface,  and  then  joint  and 
adjust  the  prepared  gold  cusps;  wax  them  in  position,  invest, 
and  flow  in  sufficient  20  k.  solder  to  hold  them  securely  in 
position,  after  which  the  tooth  may  be  ground,  adjusted,  and 
soldered  to  the  cap,  as  has  been  directed.  One  advantage  of 
this  method  is,  that  different  forms  and  shades  of  bicuspid 
facings  may  be  so  prepared — with  gold  occluding  surfaces — 
and  kept  in  stock ;  and  again,  in  the  latter  three  methods,  as 
may  be  seen,  it  is  only  necessary  to  invest  the  cap  once  after 
adjusting  the  tooth. 

Dr.  Litch's  Method. — The  method  of  Professor  Wilbur  F. 
Litch  for  forming  collar  crowns  was  first  published  in  the  Dental 
Cosmos :  (V  ol.  xxv,  p.  449),  and  was  afterwards  revised  and 
reproduced  in  the  Ajnerican  System  of  Dentistry.  In  this  Prof 
Litch  describes  his  method  as  follows  : — 

"  The  processes  to  be  described  reduces  destruction  of  tooth 
substance  to  the  minimum.  Instead  of  cutting  the  palatine  wall 
of  the  tooth  down  to  the  gum-margin,  the  greater  portion  of  it  is 
carefully  conserved,  its   presence,  while   not   indispensable  to  a 


234 


MECHANICAL    DENTISTRY. 


Fig.  219. 


Fig.  220. 


C- 


-D     E 


successful  result,  being  in  the  highest  degree  desirable.  How 
much  of  this  portion  of  the  tooth  can  be  retained  will  depend 
upon  the  nature  of  the  occlusion. 

"  In  Fig.  219  the  dotted  line  from  C  to  D  represents  the  point 

to  which  the  tooth  is  cut  away 
in  the  older  methods  of  '  pivot- 
ing :'  the  dotted  line  from  A  to 
B,  the  line  of  abscission  practised 
by  the  writer. 

"  As  will  be  seen  by  reference 
to  Fig.  220,  the  face  of  the  tooth 
thus  prepared  presents  a  gradual 
^''  slope  from  the  palatal  surface  to 

the  labio-cervical  margin.  At  the  latter  margin  the  root  should 
be  cut  down  with  suitable  instruments  to  a  point  a  little  beneath 
the  edge  of  the  gum,  in  order  that  the  porcelain  tooth  in  front 
may  pass  up  under  the  gum-margin  and  the  joint  between  the 
tooth  and  root  be  concealed.  At  this  point  tooth  substance 
may  be  sacrificed,  as  it  does  not  materially  diminish  the  strength 
of  the  root. 

"  The  several  parts  employed  in  making  the  collar  crown  are  a 
plain  plate  porcelain  tooth  or  facing,  a  platinum-iridium  retaining- 
pin,  and  a  backing,  base-plate,  and  collar  made  either  of  platinum, 
pure  gold,  or  twenty-two-carat  gold,  either  metal  being  made  in 
thickness  about  No.  30  American  gauge.  When  platinum  is 
used  coin  gold  or  twenty-carat  gold,  alloyed  with  copper  or  silver 
only,  should  be  employed  as  a  solder  and  covering.  Twenty- 
carat  gold  maybe  used  as  a  solder  when  pure  gold  is  employed, 
while  eighteen-carat  gold  will  solder  the  twenty-two-carat  plate. 
"  In  shaping  the  pulp-canal  for  the  reception  of  the  retaining- 
pin  care  should  be  taken  not  to  weaken  the  root  by  an  unneces- 
sary enlargement  of  the  caliber  of  the  canal.  The  platinum- 
iridium  pin  need  not  be  more  than  No.  14  American  gauge  in 
thickness  at  its  point  of  greatest  diameter,  near  the  free  surface 
of  the  root,  where  all  the  strain,  if  any,  falls;  from  this  point  it 
should  be  made  a  gentle  taper  corresponding  to  the  natural 
shape  of  the  space  it  is  to  occupy.  Half  an  inch  in  length  is 
ample ;  even  less  will  serve. 


ROOT    CROWNING.  235 

"The  retaining-pin  being  shaped  and  adjusted  in  the  root, 
care  being  taken  to  leave  an  excess  in  length  at  the  free  end  for 
convenience  in  subsequent  manipulations,  the  next  step  in  the 
process  is  the  making  of  the  base-plate  and  its  attachment  to  the 
pin.  A  strip  of  platinum  or  gold  of  suitable  size  is  pressed  upon 
the  face  of  the  root  with  broad-pointed,  serrated  instruments 
until  it  is  in  close  adaptation  to  the  surface  at  every  point.  This 
base-plate  is  allowed  to  project  beyond  and  overhang  the  palatine 
portion  of  the  root,  but  should  not  come  quite  to  the  labial 
edge. 

"Adaptation  being  secured,  an  opening  is  made  in  the  base- 
plate where  it  covers  the  pulp-canal,  through  which  opening  the 
retaining-pin  may  be  pressed  up  into  position  in  the  root.  Pin 
and  base-plate  are  then  removed  from  the  mouth,  dried,  and 
cemented  with  a  brittle  resinous  cement,  and  then,  while  the 
cement  is  still  plastic  and  yielding  from  heat,  placed  again  in 
position  in  and  upon  the  tooth,  and  perfect  adaptation  secured. 
While  still  in  position  in  the  mouth,  throw  upon  the  cement  a 
stream  of  very  cold  water,  so  that  it  may  be  made  brittle  and 
incapable  of  bending.  Then  remove  from  the  mouth  and  invest 
in  a  mixture  of  equal  parts  of  plaster  and  pulverized  marble, 
with  enough  water  to  make  a  thick  paste.  After  the  invest- 
ment has  set  solder  the  retaining-pin  and  the  base-plate  together. 

"  To  make  the  collar,  a  somewhat  crescent-shaped  piece  of 
platinum  or  gold  of  suitable  size  is  prepared  and  pressed  into 
shape  upon  the  palatine  and  palato-proximal  face  of  the  tooth  ; 
little  slits  may  be  cut  in  the  collar  with  a  delicate  pair  of  scissors, 
to  make  easier  this  adaptation.  Care  should  be  taken  not  to 
push  the  collar  up  under  the  gum  at  any  point, 
provided  the  palatine  wall  of  the  tooth  which  had  ^^^-  ^'^^■ 
been  allowed  to  remain  standing  is  at  all  ample  in 


height — say  one-tenth  of  an  inch;  if  less  than  this       J% 

the  collar  may  pass   under  the   gum   for  a  short  shape  of  Collar. 

distance,  as  will  be  shown  subsequently.     In  the 

average   case   this   collar   will    not    quite    one-half  encircle  the 

tooth. 

"  Fig.  221  shows  the  collar  curved  to  the  outline  of  the  gum- 
margin  and  shaped  to  the  contour  of  the  palato-proximal  wall 


236  MECHANICAL    DENTISTRY. 

of  the  tooth.     At  g  are  the  slits  cut  in  the  platinum  to  allow 
overlapping  in  shaping  to  contour. 

"  In  order  to  strengthen  the  collar  and  facilitate  its  attachment 
to  the  base-plate  cut  a  series  of  slits  in  that  portion  of  the  base- 
plate which  has  been  made  to  project  beyond  the  palatine  wall 
of  the  tooth,  and  the  base-plate,  with  its  now  attached  pin, 
being  placed  with  the  collar  in  position  in  and  upon  the  tooth, 
the  little  strips  of  metal  into  which  the  overhanging  edge  of  the 
base-plate  has  been  cut  are  pressed,  one  after  the  other,  down 
upon  the  collar  and  carefully  molded  to  its  surface,  so  that  the 
collar  will  no  longer  consist  of  a  single  thickness  of  metal,  but 
will  be  reinforced  by  these  additional  thicknesses  of  base-plate 
thus  pressed  upon  it. 

"  Fig.  222  shows  this  quite  perfectly  :  h  is  the  free  end  of  the 
retaining-pin,  which  is  to  be  cut  off  when  the  porcelain  tooth  is 
mounted,     i  is  the  base-plate,  with  its  over- 
FiG.  222.  hanging  palatine   margin    cut    into   strips,   j, 

which  are  being  pressed  down  upon  the 
collar,  F,  by  the  broad-surfaced  and  serrated 
instrument,  k.  This  being  accomplished,  re- 
move the  several  pieces  from  the  mouth, 
carefully  cement  the  collar  in  its  proper  posi- 
tion relative  to  the  base-plate,  which  will  now 
form  a  sort  of  matrix  for  it,  again  place  in  the 

mouth,  readjust,  harden  the  cement,  remove 
Pressing  the  Base-plate  .  ,         1  , 

over  the  Collar.        irom  the  mouth,  mvest  as  beiore,  and  solder 

the   collar  and   base-plate   together,    using  a 

considerable  excess  of  solder  for  covering,  so  that  the  collar  may 

be  still  further  strengthened  and  its  surface  be  made  uniform. 

"  In  cementing  the  collar  to  the  base-plate  one  precaution  is 
imperative — namely,  not  to  allow  a  film  of  cement  to  get  be- 
tween the  collar  and  the  tooth.  If  this  is  done  and  the  invest- 
ment poured  in  upon  this  film  of  cement,  the  latter  will  imme- 
diately burn  out  as  soon  as  heat  is  applied,  leaving  a  space 
between  the  collar  and  the  investment  into  which  the  gold  solder 
will  flow,  and  thus  interfere  with  that  perfect  adaptation  of  the 
appliance  to  the  tooth  which  is  necessary  to  a  successful  result. 

"The  mounting  of  the  facing,  next  demands  attention.     As 


ROOT    CROWNING.  237 

already  stated,  a  plain-plate  porcelain  tooth  is  used.     This  must 

have  what  are  technically  known  as  cross-pins  ;  that   is,  pins 

placed  at  right  angles  with  the  long  axis  of  the  tooth.     They 

must  also  be  placed  well  up  toward  the  cutting  edge.     If  they 

are  too  near  the  neck  they  will  inevitably  be  cut  out  in  fitting 

the  tooth  to   the  slope  of  the   base-plate   on   which  it  must  be 

mounted. 

"  Fig.   223    shows   the   form    of  the  facing   and   indicates  the 

slope  given  it  in  fitting.     The  fitting  process  does  not  differ  from 

that  ordinarily  employed   with  porcelain  teeth  ;  an 

impression  may  be  taken  and  the  work  done  on  a      F'°-  223. 

cast,  or  the  facing  may  be  fitted  to  the  mouth.     In 

either  case  it  is  in  the  mouth  that  the  finer  and  final 

adjustments  as  to  height,  contour,  alignment,  etc., 

must  be  perfected. 

<<  T-i  •      1     •  1  1     1        r     •         111  1      Shape  of  Porce- 

Ihis  bemg  done  and  the  facmg  backed,  tooth      lain  Facing. 

and  base-plate  are  cemented  together,  restored  to 

the  mouth,  finally  adjusted,  removed,  and  soldered  as  before,  as 

much   gold  being   flowed   into  the  angle   between  the  backing 

and  the  base-plate  as  occlusion  will  permit. 

"  This  artificial  crov/n,  being  properly  finished  and  cemented 
into  position  in  and  upon  the  tooth,  makes  what  the  writer,  from 
several  years'  experience  in  its  use  in  a  large  number  of  cases, 
has  found  to  be  an  appliance  which  will  remain  for  an  indefinite 
period  without  the  slightest  deviation  from  position  and  alignment, 
and  which  in  many  respects  is  almost  as  strong  as  the  natural 
tooth,  because  its  point  of  greatest  resistance  to  pressure  is 
placed  where  Nature  anchors  her  enamel  walls — namely,  upon 
the  outside  and  not  upon  the  inside  of  the  walls  of  dentine ;  so 
that  in  the  act  of  occlusion  the  force  applied  by  the  lower 
incisors  as  they  come  up  in  position  inside  the  upper  incisors  falls 
upon  the  uJiolc  thickness  of  the  root  tJirougli  tlie  collar,  and  not 
upon  less  than  half  its  thickness  through  a  centrally-anchored 
pin — a  pin,  too,  prolonged  into  a  lever  of  enormous  power  by  its 
attachment  to  the  porcelain  tooth. 

"  In  this  respect  there  is  a  manifest  weakness  in  all  methods 
of  mounting  artificial  crowns  which  depend  for  their  stability 
solely  upon  the  central  pin.     Ultimate  failure  through  splitting 


2 -.8 


MECHANICAL    DENTISTRY, 


Fig.  224. 


of  the  root  is  the  frequent  result,  and  the  larger  and  stronger 
and  more  deeply  anchored  the  pin  the  more  certain  this  result, 
because  a  large  pin  necessitates  a  large  opening  for  its  reception, 
and  a  corresponding  weakening  of  the  root,  upon  which  the 
strain  must  ultimately  fall :  the  lever  is  strengthened  and  the 
point  of  resistance  weakened. 

"The  only  safety  for  the  usual  form  of 'pivot-tooth'  is,  either 
that  the  occlusion  shall  be  slight,  the  root  very  strong,  or  the 
'  pivot '  very  flexible  or  elastic.  This  elasticity  of  the  old  hickory 
'pivot'  was  one  of  its  chief  excellences:  roots  were  much  less 
likely  to  split  than  with  a  rigid,  unyielding  me- 
tallic pin.  In  cuspids  or  incisors,  however, 
metallic  pins,  unless  enormously  large,  or  thickly 
packed  around  the  amalgam,  will  very  often 
bend  outward,  thus  allowing  a  slight  displace- 
ment forward  of  the  artificial  crown,  and  to  that 
extent  relieving  the  root  from  strain. 

"  Fig.  224  gives  a  sectional  view  of  the  collar- 
crown  in  position,  the  lower  incisor  being  in 
occlusion.  L  is  the  porcelain  facing,  h  is  the 
pin  attached  to  i,  the  base-plate,  m  is  the 
backing  and  solder,  n  is  the  lower  incisor,  and 
F  the  collar.  It  is  clearly  evident  that  here  the 
force  of  occlusion  falls  upon  the  palatine  wall 
of  the  natural  tooth  at  o  through  the  collar  f, 
and  not  upon  the  pin  at  the  point  of  its  attach- 
ment to  the  base-plate  h,  and  through  the  pin 
upon  the  thin  outer  shell  of  the  root. 

"  In  cases  frequently  met  with,  where  the  en- 
tire crown  of  the  tooth  has  been  removed,  the  collar,  as  before 
described,  can  be  adapted  to  the  palatine  face  of  the  root,  pro- 
vided the  latter  be  not  decayed  away  up  to  the  alveolar  margin. 
Usually,  however,  there  is  a  considerable  space  between  the  free 
edge  of  the  root  and  the  alveolus,  and  here,  running  up  to  the 
alveolus,  the  collar  must  be  placed. 

"  The  dotted  line  e  in  Fig.  220  indicates  a  collar  so  placed. 
All  the  steps  in  the  process  are  essentially  the  same  as  before 
described.     Adapting  the  collar  to  the  surface  of  the  root  be- 


Sectional  view  of 
collar-crown  in 
position,  the 
lower  incisor  in 
occlusion. 


ROOT    CROWNING.  239 

neath  the  gum  is  somewhat  painful,  but  not  excessively  so,  and  in 
the  wearing  the  irritation  caused  by  its  presence  is  very  slight  and 
transient  in  character,  assuming,  of  course,  that  care  has  been 
taken  to  leave  upon  it  a  smooth,  thin,  and  well-polished  edge. 

"  The  objection  may  be  urged  that  this  form  of  crown  resists 
pressure  only  in  one  direction,  from  within  outward,  and  does  not 
provide  for  lateral  pressure  or  pressure  from  the  front.  As  a 
rule,  the  latter  can  occur  with  any  force  only  as  the  result  of  ac- 
cident, while  if  the  crowned  tooth  is  in  normal  relation  with  its 
fellows,  and  the  artificial  crown  be  closely  fitted  between  them, 
they  will  fully  sustain  lateral  force. 

"  Where  such  lateral  support  is  wanting  through  isolation  of 
the  tooth,  the  collar  must  be  extended  into  a  ring  or  ferrule  com- 
pletely encircling  and  grasping  the  root,  and  thus  affording  sup- 
port on  all  sides.  The  ring,  however,  is  more  troublesome  to 
make  and  more  painful  to  apply,  and  generally  shows  a  line  of 
gold  in  front.  In  the  average  case  the  simple  collar  gives  all 
requisite  strength. 

"  In  mounting  crowns  upon  bicuspid  and  molar  roots,  however, 
the  ferrule  principle  is  often  essential  to  stability  ;  especially  is 
this  true  of  lower  bicuspids  and  molars  ;  as  here  the  forces 
applied  in  mastication  are  as  erratic  in  direction  as  they  are 
powerful  in  character,  and  the  root  must  be  guarded  at  every 
point  against  their  violence. 

"  In  fixing  in  position  the  artificial  crowns  just  described,  the 
writer  prefers  to  use  a  gutta-percha  cement  adhesive  in  character, 
which  w^ill  not  strip  from  the  pin  when  the  crown  is  forced  into 
position. 

"  The  apical  foramen  is  closed,  the  pulp-canal  grooved  and 
thoroughly  dried,  the  central  pin  is  barbed,  and  the  pin  and  inside 
of  the  collar  and  under  surface  of  the  base-plate  are  thickly 
coated  with  the  gutta-percha  ;  the  entire  appliance  is  then  heated 
to  a  temperature  sufficient  to  thoroughly  soften  the  gutta-percha, 
and  firmly  pressed  up  into  position  :  the  excess  of  gutta-percha 
will  ooze  out  at  all  free  margins,  and  may  be  subsequently  removed 
with  suitable  instruments. 

"A  good  gutta-percha  cement  will  hold  firmly  in  a  great  ma- 
jority of  cases,  but  when,  as  in  a  small  lateral  incisor,  the  retain- 


240 


MECHANICAL    DENTISTRY. 


ing-pin  is  necessarily  small  and  short  and  the  collar  not  as  ample 
as  could  be  desired,  an  oxyphosphate  cement,  mixed  thin, 
will  be  found  to  give  greater  stability.  When  this  cement  is 
used,  however,  it  will  be  found  very  difficult  to  detach  the  arti- 
ficial crown  from  the  root,  should  it  for  any  reason  become 
necessary  to  do  so  ;  whereas  a  little  heat  will  quickly  soften  a 
gutta-percha  packing  and  permit  the  entire  appliance  to  be  with- 
drawn without  difficulty." 

As  a  modification  of  the  manner  of  constructing  the  collar, 
Dr.  Theodore  F.  Chupein  contributes  the  following  to  the  Dental 
Cosmos  : — 

"  After  the  root-face  has  been  dressed  down  as  shown  in  Fig. 
220,  a  piece  of  pure  gold  plate  of  No.  30  gauge  is  cut  as  shown  in 

Fig.  225. 


Fig.  225.  This  is  bent  around  the  root,  as  shown  in  Fig.  226,  the 
wide  part  resting  against  its  palatal  aspect,  while  the  ends  are  seized 
with  a  pair  of  narrow-beaked,  flat-nosed  pliers  at  the  labial  aspect. 
While  thus  held,  the  band  may  be  burnished  to  fit  accurately 
against  the  approximal  and  palatal  parts  of  the  root.  This  done, 
it  is  removed  and  the  ends  soldered  together,  as  shown  in  Fig. 
227.  This  band  is  then  replaced  on  the  root,  and,  as  it  hugs  the 
root  snugly,  any  of  the  edges  which  may  be  higher  than  the  face 
of  the  root  may  be  ground  down  even  with  a  corundum 
stump-wheel.  It  is  again  removed  from  the  root  and  laid 
on  a  piece  of  pure  gold  plate  of  the  same  thickness,  to  which 
it  is  soldered,  as  in  Fig.  228.  The  overhanging  edges  of  the 
plate,  as  soldered  to  the  collar,  are  now  dressed  down  even 
with  the  collar,  and  the  forward  part  of  the  collar  filed  or  ground 
away  from  the  plate,  as  shown   in   Fig.   229.     A   hole   is  now 


ROOT    CROWNING,  24 1 

drilled  or  punched  through  the  face-plate  to  receive  the  dowel, 
which  passes  through  it  into  the  root.  The  under  part  of  the 
face-plate  at  the  hole  should  be  well  countersunk,  so  that  the 
solder  that  binds  the  dowel  to  the  face-plate  may  creep  through 
and  hold  the  dowel  on  its  under  surface.  The  face-plate  and 
collar,  as  shown  at  Fig.  229,  are  placed  on  the  root  and  burnished 
down  to  fit  accurately  at  all  points.  A  slight  smearing  of  ce- 
ment is  placed  over  the  dowel-hole,  so  as  to  fill  the  countersink, 
and  the  dowel  passed  through  and  secured  to  the  face-plate  with 
more  cement.  Before  this  hardens  it  is  placed  on  the  root  in  its 
proper  position,  after  which  the  cement  is  chilled  by  a  stream  of 
cold  water,  when  it  is  removed,  invested,  and  soldered.  Fig.  230 
shows  the  collar,  face-plate,  and  dowel  complete.  This  being 
accomplished,  the  face-plate  is  slightly  reduced  on  its  labial 
aspect,  so  as  to  expose  the  root  against  which  the  porcelain 
facing  is  to  rest.  The  protruding  part  of  the  dowel  is  now  cut  off 
level  with  the  face-plate,  and  the  porcelain  tooth  fitted  to  it. 
This  part  of  the  operation  does  not  differ  from  that  indicated  by 
Prof.  Litch,  and  therefore  need  not  be  repeated  here. 

"The  operation  as  set  forth  consumes  much  less  time,  is  less 
tedious,  does  not  demand  the  nice  manipulative  ability  of  the 
other,  and  is  more  certain  in  its  results." 

Dr.  Knapp's  Process. — No  individual  method  has,  perhaps 
more  immediately  and  generally  commanded  the  approval  and 
commendation  of  expert  and  discriminating  operators  than  the 
one  brought  to  the  notice  of  the  profession  by  Dr.  J.  Rollo 
Knapp,  of  New  Orleans,  La.  Omitting  some  judicious  and  per- 
tinent general  reflections  on  the  subject  (see  Dental  Cosmos,  of 
Feb.,  1887),  all  that  relates  to  practical  details  in  his  methods  of 
procedure  is  here  reproduced. 

"  The  collar  being  removed,  its  gingival  border  must  be  care- 
fully filed  so  as  to  adjust  it  exactly  to  the  various  inequalities 
existing  in  the  borders  of  the  alveolar  process  and  its  investing 
gum.  The  other  border  should  then  be  evenly  filed  down  so  as 
to  reduce  the  collar  to  the  requisite  narrowness.  A  piece  of 
pure  gold  plate,  gauge  thirty-four,  is  now  to  be  soldered  upon 
this  latter  border  so  as  to  convert  the  collar  into  a  cap  for  the 
root.  This  cap  must  have  pierced  in  it  such  an  aperture  as 
16 


242 


MECHANICAL    DENTISTRY. 


will  conform  to  the  configuration  of  the  pin  or  dowel  best  suited 
to  the  particular  case  in  hand.  Cap  and  pin  waxed  together, 
should  then  be  tried  in  the  mouth,  carefully  removed,  invested 
in  calcined  marble-dust  and  plaster,  and  soldered.  Being  again 
placed  upon  the  root,  an  impression  of  it  should  be  taken,  as 
well  as  of  the  two  approximal  teeth." 

A  set  of  small  trays  especially  made  for  the  purpose  will  be 


Fig.  231. 


Fig.  232. 


Fig.  233. 


Fig.  234. 


Fig.  235. 


Fig.  236. 


found  very  convenient  for  taking  impressions  for  crown-work, 
Figs.  231  to  237.  Plaster  or  modeling  composition  can  be  used 
in  doing  this.  Upon  its  being  ascertained  that  the  cap,  with  pin 
attached,  is  in  its  proper  position  in  the  impression,  a  plaster  cast 
can  be  obtained,  which,  with  a  cast  of  the  occluding  teeth,  should 
be  placed  in  an  articulator. 

While  the  writer  believes  it  to  be  the  most  accurate,  when 
making  single  crowns,  to  grind  and  adjust  the  tooth  in  the 
mouth,  it  frequently  happens,  from  lack  of  time  or  other  reasons, 
that  it  is  not  practicable;  then  the  impression  should  be  taken  as 
directed. 


ROOT    CROWNING. 


243 


From  this  point  succeeding  steps  will  differ  according  to  the 
character  of  crown  to  be  inserted.  If  it  be  an  incisor,  which  is 
to  have  a  porcelain  front,  a  plain  plate  tooth  of  suitable  size, 
shape,  and  shade  should  be  backed  with  pure  gold,  ground  to 
position  upon  the  anterior  portion  of  the  cap,  and  united  to  it 
by  adhesive  wax.  Sufficient  wax  should  be  used  to  perfectly  re- 
store the  contour  and  to  produce  the  most  accurate  kiutckling  or 
adjustment  of  the  approximal  surfaces  of  the  teeth.  Too  much 
stress  cannot  be  laid  upon  this  latter  point, — one  not  usually 
attended  to.  Yet  all  the  reasons  for  observing  it  in  all  other 
kinds  of  contour  work  are  no  less  potent  here.  In  this  proce- 
dure pure  gold    of  thirty-four  gauge  should  be  made  to  com- 


FiG.  237 


pletely  envelop  the  sides  and  incisive  portion  of  the  wax,  includ- 
ing the  edges  of  the  backing  and  contiguous  portions  of  the  cap. 
All  should  now  be  invested,  the  wax  removed  by  boiling  water, 
drying  effected  by  a  gentle  heat,  and  the  resulting  golden  pocket 
filled  with  twenty-carat  solder.  The  solder,  previously  cut  in 
small  squares,  is  to  be  dropped  into  the  mouth  of  the  mold,  and 
sprinkled  with  a  very  little  powdered  borax, — repeating  this 
process  with  the  left  hand  as  fast  as  the  solder  is  melted  under 
the  blowpipe  while  held  in  the  right  hand  until  the  mold  is 
quite  filled.  To  accomplish  this  in  the  best  manner  the  flame 
of  the  blowpipe  should  be  quite  intense,  but  at  the  same  time 
exceedingly  small. 

The  small  and  deep  mold  formed  by  the  gold  shell  enveloped 
in  the  marble  and  plaster  matrix  has  a  very  narrow  opening, 
which  renders  necessary  an  intense  heat,  capable  of  concentra- 


244  MECHANICAL    DENTISTRY. 

tion  upon  and  easy  application  to  the  innermost  recesses  of  the 
mold,  which  is  to  be  filled  with  molten  gold.  An  oxy-hydrogen 
blowpipe*  was  therefore  constructed  to  utilize  the  condensed 
nitrous-oxide  gas  in  combination  with  common  illuminating  gas 
for  the  production  of  a  mixture  which  is  conducted  through  a 
thin  rubber  tube  of  one-eighth  inch  bore  to  a  very  small  blow- 
pipe, which  emits  a  steady  flow  of  constantly  ignited  gas  in  the 
form  of  a  pointed  pencil  about  half  an  inch  in  length  by  one- 
quarter  of  an  inch  at  its  greatest  diameter.  With  this  blowpipe 
in  hand,  the  plaster  matrix  may  be  speedily  heated  by  playing 
the  stream  of  fire  over  its  surface  until  the  mass  is  aglow,  when 
the  point  of  the  flame  is  thrown  into  the  mold  by  rapid  thrusts 
until  the  solder  melts  like  wax  and  fills  every  part  of  the  mold 
with  liquid  gold.  From  the  first  application  of  the  flame  to  the 
previously  dried  and  warmed  matrix,  there  is  usually  no  more 
than  ten  minutes  consumed  in  bringing  the  solder  to  the  fusing 
point  and  completing  the  cast  of  gold  in  the  little  mold.  It 
would  seem  that  by  such  means  only  can  the  requisite  heat  be 
obtained,  directed  and  controlled  with  the  sensitiveness  of  adjust- 
ment that  admits  of  the  twenty-carat  solder  being  melted  in, 
yet  without  destruction  of,  the  thin  gold  crucible  within  the 
matrix.  After  cooling,  removing  investient,  and  boiling  in  acid, 
superfluous  solder  can  best  and  most  expeditiously  be  removed 
by  corundum-wheels  on  the  engine.  Care  should  be  taken  not 
to  cut  away  the  gold  forming  the  approximal  knuckling,  and  to 
artistically  carve  the  palatal  portion. 

Fig.  238  represents  a  band  of  collar-gold,  twenty-two  carats 
fine,  twenty-eight  gauge ;  Fig.  239,  a  soldered  collar  or  ferrule 
made  from  it ;  Fig.  240,  a  square  gold  pin,  twenty-carats  fine  ; 
Fig.  241,  a  plate  of  pure  gold,  thirty-four  gauge,  for  a  cap ;  Fig. 
242,  the  collar,  cap,  and  pin  duly  invested.  Fig.  243,  represents 
the  collar,  cap,  and  pin  soldered  together  with  twenty-carat 
solder;  Fig.  244,  a  lateral  incisor  plate-tooth,  backed  with  pure 
gold,  twenty-eight  gauge,  ground  to  the  anterior  portion  of  the 
cap,  fastened  to  it  with  wax,  contoured  to  represent  a  natural  in- 
cisor, the  approximal  sides  as  well  as  incisive  portion  of  which, 

*  See  p.  49,  Fig.  26. 


ROOT    CROWNING. 


245 


together  with  the  edges  of  the  gold  backing  and  contiguous 
parts  of  the  cap,  all  enveloped  in  pure  gold,  thirty-four  gauge. 
Fig.  245  represents  the  same,  invested  in  calcined  marble-dust 
and  plaster,  the  wax  removed,  disclosing  the  golden  pocket 
ready  for  the  reception  of  the  solder.  Fig.  246  shows  the  crown 
after  the  soldering  has  been  effected  ;  Fig.  247,  the  lateral  incisor 
crown  divested  of  superfluous  solder  and  completely  finished. 

In  constructing  a  cuspid,  its  natural  palatal  characteristics 
should  be  as  accurately  reproduced  as  practicable,  Figs,  248,  249, 
250,  251,  252.     The  formation  of  a  porcelain-faced    bicuspid  is 

Fig.  244.  Fig.  245.      Fig.  246.  Fig.  247.       Fig.  248.  Fig.  249. 


Fig.  250.       Fig.  251.  Yic.  252.         Fig.  253.        Fig.  254.  Fig.  255. 


similar  to  that  which  has  just  been  detailed,  up  to  the  soldering 
of  the  backed  tooth  to  the  cap.  Fig.  253.  The  subsequent 
stages,  however,  are  very  different.  The  perfect  configuration 
of  a  bicuspid  should  be  reproduced  in  wax,  aptness  of  occlusion 
and  knuckling  being  carefully  attended  to,  Fig.  254.  In  this 
condition  the  crown  should  be  placed  in  a  small  ring,  such  as  is 
shown  in  Fig.  255,  first  set  with  wax  in  the  desired  position,  and 
then  secured  there  by  plaster.  The  exposed  portion  of  the 
crown  and  surrounding  plaster  should  then  be  coated  with  san- 
darac  varnish  and  molded  in  marble-dust  and  glycerin,  contained 


246 


MECHANICAL    DENTISTRY. 


in  a  corresponding  annular  section,  Fig.  256.  Over  this  is  to  be 
placed  a  conical  tube,  such  as  is  represented  in  Fig.  257,  and  into 
which  molten  zinc  is  to  be  poured.  With  the  die.  Fig.  258, 
thus  cast,  in  accurately  reproducing  the  natural  cusps  and  sulci, 
there  can  be  obtained  with  pure  gold  plate,  thirty-four  gauge,  a 
perfect  counterpart  of  the  grinding  surface  of  a  bicuspid  crown, 
Fig.  259.  The  palatal  cavity  of  the  impression  thus  made  in 
the  plate  must  now  be  filled  with  gold  solder,  twenty  carats  fine, 
after  which  the  piece  must  be  finished  up  by  any  requisite  trim- 
ming. Care  should  be  taken  to  leave  the  palatal  cusp  entire, 
and  just  enough  of  the  buccal  or  external  cusp  to  combine  with 


Fig.  256. 


Fig.  257. 


Fig.  258. 


Fig.  259. 


Fig.  260. 


Fig.  261. 


the  porcelain  face  in  the  formation  of  a  proper  occluding  surface, 
Fig.  260.  From  the  model,  as  represented  in  Fig.  254,  sufficient 
wax  must  now  be  displaced  to  permit  of  the  prepared  gold  cusps 
assuming  their  proper  position,  and  the  approximal  surfaces  re- 
maining in  the  wax  then  enveloped  with  pure  gold,  thirty-four 
gauge.  The  palatal  portion  of  the  collar  must  be  protected  with 
a  strip  of  pure  gold,  twenty-eight  gauge,  one-sixteenth  of  an 
inch  in  width.  All  is  now  ready  to  be  invested.  Fig.  261.  After 
removal  of  the  wax,  through  the  palatal  aperture  remaining,  the 
internal  walls  of  gold  will  be  disclosed.  Fig.  262.  By  careful 
manipulation  with  the  small  and  intense  blowpipe  flame  before 
mentioned,  twenty- carat  solder  can  be  so  flowed  in  as  to  make  a 


ROOT    CROWNING. 


247 


solid  golden  mass,  from  which  can  be  readily  shaped  a  perfect 
bicuspid.  Fig.  263. 

In  the  construction  of  an  all-gold  bicuspid  crown  some  of  the 
steps  differ  from  those  just  described.  Upon  the  cap  are 
dropped   several  beads  of  wax.     From  this  shapeless  mass  is 


Fig.  262.        Fig.  263.       Fig.  264.  Fig.  265.  Fig.  266. 


Fig.  268. 


carved  a  perfect  bicuspid,  Fig.  264.  A  die  is  then  obtained, 
Fig.  265,  after  the  manner  just  detailed.  A  grinding  surface  is 
swaged  in  pure  gold,  Fig.  266,  and  the  cusps  are  filled  with 
twenty-carat  solder.   Fig.    267,  and   placed   in    proper   position 


Fig.  269.  Fig.  270.         Fig.  271. 


Fig.  27: 


upon  the  wax  tooth.  A  piece  of  pure  gold  plate,  slit  at  the 
edges  for  facilitating  adjustment,  should  now  be  made  to  cover 
about  two-thirds  of  the  yet  exposed  border  of  wax,  Fig.  268. 
After  being  invested,  and   the  wax  removed  by  hot  water,  a 


248  MECHANICAL    DENTISTRY. 

suitable  aperture  is  left  for  soldering,  Fig.  269.  The  resulting 
completed  bicuspid,  true  to  nature,  is  seen  in  Fig.  270.  The 
descriptions  just  given  answer  for  all-gold  molars,  Figs.  271,  272, 

273.  274. 

In  carving  the  cusps  and  sulci,  and  in  otherwise  modeling  the 
gold  parts  of  the  crowns,  small  engine  corundum-wheels  and 
points,  varying  from  coarse  to  fine,  and  barely  moistened,  to  in- 
sure accuracy  and  delicacy  of  touch,  are  preferable  to  files  or 
any  form  of  steel  instruments.  The  smoothing  and  polishing  is 
done  with  wet  felt-wheels,  fine  pumice,  pulverized  silex,  moose- 
hide  points  with  chalk,  brush-wheels  and  whiting,  and  finally 
with  rouge.  It  is  a  matter  of  much  importance  that  great  care 
should  be  exercised  in  the  preparation  of  the  gold  used.  The 
solder  should  be  uniform,  flow  easily,  and  conform  well  in 
color  to  the  work  in  hand. 

Dr.  Shields'  System. — The  following  methods,  taken  from 
a  recent  issue  of  the  Dental  Cosmos,  is  contributed  by  Drs.  N.  T. 
and  L.  N.  Shields.     They  write  in  part  as  follows : — 

The  points  in  this  work  to  which  we  desire  to  direct  attention 
are  its  permanency,  absolute  cleanliness,  and  artistic  beauty.  By 
the  methods  herein  described  the  crowns  are  constructed  upon 
anatomical  lines,  larger  at  the  grinding-  and  cutting-surfaces,  so 
as  to  admit  of  thorough  mastication  of  food  without  injury  to  the 
gums.  The  ordinary  shell  crowns  are  positively  wrong  in  shape 
and  construction,  because  the  normal  crown  has  a  larger 
diameter  than  the  neck  of  the  tooth,  therefore  a  band  made  to 
fit  the  crown  of  a  tooth  tightly  will  be  too  large  at  the  neck.  This 
will  necessarily  leave  a  space  for  the  lodging  of  food  debris  (al- 
though it  may  go  under  the  gum),  will  make  the  gum  present  a 
very  unnatural  appearance,  will  make  the  gold  tooth  altogether 
unnatural  in  construction,  and  the  result  after  a  very  few  years 
will  be  a  mass  of  decay  under  the  shell  crown,  which  makes  it 
not  only  a  temporary  operation,  but  a  constitutionally  as  well  as 
a  locally  injurious  one. 

The  enamel  widens  or  becomes  thicker  the  nearer  it  approaches 
the  grinding-  and  cutting-surfaces,  and  in  order  to  get  a  perfect 
junction  of  the  collar  crown  and  the  neck  of  the  tooth  we  must 
remove  all  enamel.     Their  procedure  is  as  follows  :   First  destroy 


ROOT    CROWNING. 


249 


Fig.  275.     Fig.  276.        Fig.  277. 


the  vitality  of  the  pulp,  then  extract  all  of  it  with  Donaldson's 
nerve-canal  cleansers.  With  a  little 
patience  and  using  No.  5  all-fine, 
and  for  every  sitting  a  new  cleanser, 
every  particle  should  be  removed 
from  the  roots,  when  they  should 
be  perfectly  filled  to  their  respective 
apices.  This  done,  the  whole  crown 
is  cut  off  almost  even  with  the  gum ; 
there  will  still  be  a  thin  portion  of 
the  enamel  left  surrounding  the 
root,  and  this  can  easily  be  re- 
moved by  using  the  No.  2  and  No.  3  scalers  made  by  the  S.  S. 
White  Dental  Mfg.  Co.  (See  Figs.  275  and  276).  This  done, 
shape  the  root  for  a  solid  all-gold  crown,  as  shown  in  Fig.  277. 
The  procedure  in  the  case  of  porcelain-faced  crowns  will  be 
described  later. 

Around  this  conically  shaped  root  (the  removal  of  the  enamel 
alone  will  generally  shape  it  sufficiently)  fit  a  twenty-two-carat 
gold  band  so  as  to  come  in  contact  with  all  parts  of  the  conical 
portion  of  the  root,  which,  when  made,  naturally  gives  a  conical 
band.  To  make  this  band,  first  make  a  tin-foil  model,  as  seen  in 
Fig.  278  ;  this  causes  less  pain  to  the  patient.  From  this  an 
absolute  shape  in  gold  is  obtained  more  quickly,  and  a  saving 
of  gold  results.  This  band  is  soldered  with  twenty-two-carat 
solder,  then  placed  in  position,  and  its  free  margins  ground 
down  even  with  the  root-end. 

Next  prepare  the  band  for  a  pure-gold  floor  by  taking  a 
Butler  corundum-point  and  hollowing  out  the  upper  or  small 
end  by  beveling  from  the  inside  edge  so  as  to  allow  room  for  the 
solder.  Although  only  an  infinitesimal  amount  of  solder  runs 
inside,  still  there  must  be  a  place  for  that  little  to  flow  ;  other- 
wise the  band  could  not  go  back  into  place,  on  account  of  the 
solder  flowing  inside,  and  we  must  have  the  solder  to  flow  inside 
in  order  to  make  a  complete  cone  externally.  Now  take  a  piece 
of  pure  gold  (No.  34  American  gauge)  and  cut  just  a  little  larger 
than  the  band,  anneal  it,  and  adapt  it  perfectly,  then  place  the  two 
in  a  No.  7  Melotte  soldering-clamp  (Fig.  279),  and  be  sure  they 


250  MECHANICAL    DENTISTRY. 

do  not  move  ;  place  borax,  mixed  with  water  to  a  thin  cream, 
all  around  the  overlapping  edge  of  pure  gold,  place  a  small 
piece  of  twenty-two-carat  gold  solder  at  the  junction  of  the  band 
and  floor,  and  with  a  broad,  gentle  flame  solder  the  entire  floor 
with  the  one  piece  of  solder  and  at  the  same  moment.  The 
clamp  holds  them  firmly  together,  and  the  work  can  be  placed 
back  on  the  tooth  without  rocking.     (Fig.  280.) 

Now  make  the  pivots  or  dowels  (of  platinum  and  iridium  wire), 
and  roughen  them  before  placing  in  position.  Drill  holes  corre- 
sponding with  the  root-canals,  place  the  pivots  in  position,  and 
fasten  them  to  the  floor  with  prepared  hard  wax.  Now  remove 
carefully,  and  invest  pivots,  floor,  and  band  in  equal  parts  of 
plaster  and  marble-dust,  and  after  removing  the  wax  with  boiling 
water,  unite  them  with  twenty-two-carat  gold.     Now  cut  down 


Fig.  279, 


the  overlapping  pure-gold  floor  exactly  even  with  the  band,  also 
cut  down  the  projecting  ends  of  the  pivots.  This  constitutes 
the  foundation  for  a  solid  gold  crown.  Never  make  pivots  for 
canals  which  cannot  be  thoroughly  filled  with  cement.  It  is 
better  to  shorten  the  pivot  somewhat  and  make  it  thicker,  and 
depend  for  anchorage  only  upon  the  lower  part  of  the  canal,  as 
shown  in  Fig.  281. 

Now  put  the  foundation  in  its  position  in  the  mouth  (upper 
jaw,  for  example),  and  take  an  impression  of  the  whole  upper  jaw 
in  modeling  compound,  also  take  an  impression  of  the  whole 
lower  jaw.  Remove  the  foundation,  and  place  it  with  great 
care  exactly  in  its  proper  matrix  in  the  impression  just  taken, 
then  stay  it  to  the  modeling  compound  with  wax  in  two  or  three 
places ;  be  careful  not  to  move  it  with  the  wax  knife,  dry  the 
pivots  and  band  on   the  inside,  and  cover  the  pivots  with  a  film 


ROOT    CROWNING. 


251 


of  wax,  also  run  a  film  of  wax  around  the  band  on  the  inside, 
but  be  sure  to  remove  all  wax  from  the  edge  ofthe  band,  because 
we  want  that  to  rest  firmly  upon  the  plaster.  Now  fill  the  im- 
pression with  plaster  to  make  a  model. 

After  separating  the  model,  remove  the  crown  foundation  from 
the  model  by  making  a  hole,  usually  on  the  palatal  surface,  with 
a  pocket-knife,  through  the  plaster  to  the  apical  end  of  the 
pivot.  Now  place  the  model  and  foundation  in  hot  water, 
and  with  a  little  pressure  on  the  end  of  the  pivot  the  whole 
foundation  is  easily  removed.  Syringe  out  all  wax  from  the 
model  and  foundation ;  the  latter  should  then  be  replaced  upon 
the  model. 

Next  make  the  stamp  for  a  grinding-surface  ;  use  for  this  pure 
gold,  34  American  gauge,  and  fill  in  the  cusps  with  twenty-two- 

FiG.  280.    Fig.  2S1.        Fig.  282.        Fig.  283.  Fig.  284. 


carat  solder.  Melotte  makes  a  very  fine  set  of  steel  stamps  that 
one  can  generally  make  use  of,  but  a  zinc  cast  can  be  made  in  a 
few  minutes  by  simply  placing  White's  prepared  molding-sand, 
always  ready  for  use,  in  a  ring  and  gently  embedding  the  grind- 
ing-surface of  a  suitable  tooth,  and  in  a  minute  by  the  watch  a 
small  quantity  of  zinc  can  be  melted  and  poured  into  the 
impression  in  the  sand.  The  molar  or  bicuspid  stamp  is  made 
in  the  usual  way  by  placing  the  pure  gold,  always  well  annealed, 
on  a  piece  of  lead  and  striking  a  few  light  blows  on  the  die, 
which  gives  a  perfect  grinding-surface,  as  seen  in  Fig.  282. 
This  is  the  reverse  side  of  a  stamp  of  a  superior  left  first 
molar. 

Next  trim  off  all  surplus  gold,  leaving  the  grinding-surface  as 
represented  in  the  cut.  The  cusps  are  next  filled  with  twenty- 
two-carat  solder.     The  reason  twenty-two-carat  solder  is  used 


252  MECHANICAL    DENTISTRY. 

is,  when  the  whole  space  between  the  <^rinding-surface  and  the 
foundation  is  filled  in  with  twenty-carat  solder  there  is  no  danger 
of  the  twenty-two-carat  being  melted  out  of  the  cusps,  and  con- 
sequently no  danger  of  having  an  air-bubble  just  under  the 
grinding  surface  which,  of  course,  would  make  itself  visible  after 
a  k\v  days'  use. 

Having  taken  a  full  impression  of  both  upper  and  lower  jaws, 
an  absolutely  correct  articulation  is  secured.  Now  add  wax  to 
the  foundation,  which  can  be  removed  from  the  plaster,  until  an 
exact  articulation  with  the  pure-gold  grinding-surface  is  pro- 
duced. After  having  gotten  this  with  hard  wax  so  that  it  may 
be  manipulated  without  disturbing  its  position,  continue  to  build 
out  the  tooth  to  its  anatomically  correct  contour  with  wax, 
frequently  trying  it  into  place.  After  the  foundation  is  removed 
from  the  plaster,  the  plaster  is  cut  away  from  between  the 
foundation  and  the  adjoining  teeth  without  disturbing  the 
plaster  upon  which  the  band  rests.  When  this  plaster  is  re- 
moved, wax  is  added  up  to  the  very  edge  of  the  band,  so  that 
the  entire  anatomical  contour  can  be  restored  with  gold,  includ- 
ing even  that  of  the  enamel  chipped  off  at  the  cervical  margin. 
The  wax  tooth  should  always  be  tried  in  the  mouth,  to  be  sure 
that  everything  pertaining  to  form,  contour,  and  position  is  just 
right.  This  was  the  object  of  removing  the  foundation  from 
the  plaster  model  at  the  outset,  as  it  is  a  great  advantage,  and 
particularly  so  with  facings,  to  always  just  at  this  time  try  the 
tooth  in  the  mouth. 

Now  from  a  piece  of  tin  foil  (No.  60)  a  model  is  cut  so  as  to 
fit  the  wax  exactly.  We  cut  the  gold  on  the  palatal  surface 
from  the  height  of  foundation  (see  A,  Fig.  283),  thereby  enabling 
us  to  join  the  free  ends  at  the  cervico-palatal  surface.  The 
large  ends  of  the  gold  we  turn  out  and  back,  to  stay  it  in 
the  investment  of  plaster  and  marble-dust.  The  gold  can  be 
cut  a  little  long,  to  allow  of  bringing  the  cervical  ends  together. 
This  cervical  margin  is  very  important,  as  shown  in  Fig.  284. 
Sometimes  three  pieces  of  gold  are  used  instead  of  one,  but  if 
so  the  pieces  of  gold  should  always  be  cut  with  projections  (as 
seen  in  Fig.  283)  to  retain  the  exact  shape  of  the  tooth  and  not 
pull  it  from   the    instrument  when   soldered.     This  gold  band 


ROOT    CROWNING.  253 

must  fit  just  under  the  edge  of  the  grinding-surface  stamp, 
and  be  in  perfect  contact  with  it,  so  as  not  to  allow  the 
grinding-surface  to  move.  This  little  thickness  of  pure  gold 
(No.  34  American  gauge),  must  be  allowed  for  waxing  up 
the  tooth. 

Now  we  have  the  wax  tooth  thoroughly  boxed  in,  excepting 
the  palatal  surface.  Before  taking  the  next  step,  be  sure  that 
the  pure  gold  band  for  boxing  is  in  contact  with  the  cervical 
margin  of  the  foundation-band.  At  the  point  of  junction  here 
and  at  the  grinding-surface  place  a  little  wax,  and  then  cut  all 
possible  surplus  away,  leaving  only  the  very  junction  filled;  also 
be  sure  no  wax  gets  on  the  inside  of  the  cervical  margin  of  the 
foundation-band.  Now  place  the  tooth  in  water  and  invest  it  in 
plaster  and  marble-dust,  covering  the  whole  tooth  except  the 
palatal  surface  of  the  crown  ;  the  plaster  must  just  cover  the 
narrow  gold  joined  at  the  cervical  margin.  After  the  plaster 
sets,  boil  out  the  wax  and  cut  the  investment  as  small  as  possi- 
ble, leaving  the  plaster  only  about  one-eighth  of  an  inch  all 
around.  Now  dry  thoroughly,  but  not  in  contact  with  a  flame; 
have  something — a  top  of  a  tin  box,  for  instance — between  the 
flame  and  the  tooth.  After  it  is  dry,  place  it  in  the  flame  of  a 
small  Bunsen  burner.  To  hasten  the  heating-up  process,  a  foot 
blowpipe  may  be  used  to  get  it  red  hot  very  quickly,  but 
nevertheless  the  heating  up  is  to  be  done  cautiously,  and 
during  this  time  we  still  have  the  little  Bunsen  flame  under 
it.  Now  by  applying  the  flame  of  the  Knapp  blowpipe  the 
gold  flows  with  the  greatest  ease  in  all  parts  and  in  all  direc- 
tions. Here  use  twenty-carat  solder.  Fill  the  molar  about 
half  full  with  gold,  using  borax  as  a  flux,  before  using  the 
Knapp  blowpipe. 

It  should  be  observed  that  we  have  the  solder  almost  to  the 
melting  point,  everything  is  red  hot,  and  a  hot  flame  beneath  the 
investment,  so  that  when  we  gently  apply  the  Knapp  blowpipe 
flame  the  gold  simply  drops,  and  while  in  this  molten  condition 
add  the  rest  of  the  solder,  never  allowing  it  to  cool  for  one 
moment,  for  if  it  does  air-bubbles  will  result.  Here  the  eold 
boxing-band  at  the  cervico-palatal  margin  does  its  work  beauti- 


254  MECHANICAL    DENTISTRY. 

fully;  the  gold  flows  freely  all  around,  with  no  danger  of  solder 
running  inside  the  foundation  from  the  palatal  side.     The  plaster 
and  marble-dust  should  always  be   worked  as  stiff  as  possible, 
so  as  to  always  have  the  gold  in  contact  with  plaster, 
'       which  will  not  be  the  case  if  the  investment  is  mixed 
/l    //  \      thin.     The  necessity    of  having   everything   firmly 
\  \j/     I     held,  so  that  the  gold  solder  will  not  pull  it  in  and 
change  the  entire  shape  of  the  crown,  becomes  evi- 
dent when  the  large  amount  of  solder  used  is  con- 
sidered.    This   being    a   solid   crown,   we  put  it    in 
water  to  cool,  and  next  in  very  dilute  sulphuric  acid, 
and  gently  heat  it  to   remove    adhering  borax   and  oxidation. 
Now  we  can  shape  the  gold  to  anatomically  correct  contour 
lines  and  bring  the  cervical  margin  down  to  a  feather-edge,  so 
that  when  again  placed  on  the  root  we  have  an  absolute  junc- 
tion without   a   lodging   place  for  acids,  and  the  whole  tooth 
restored  to  a  state  of  perfection.     (See  Fig.  285). 

In  the  construction  of  a  crown  with  a  porcelain  face,  the 
root  is  shaped  just  as  for  a  solid  crown,  excepting  that  it  is 
cut  under  the  gum  on  the  labial  surface,  and  also  lower  on 
the  palatal  surface,  so  as  to  remove  all  enamel  (Fig.  286). 
After  cutting  under  the  gum  hold  the  gum  back  by  anchor- 
ing premium  gutta-percha  in  the  root-canal  and  press  it  over 
the  labial  surface.  After  the  crown  has  been  set,  the  gum 
comes  down  beautifully  over  the  gold  band  and  prevents  its 
being  visible.  Prepare  and  complete  the  foundation  the  same 
as  for  the  solid  crown,  taking  impressions,  bite,  etc.,  as  before, 
and  select  the  shade.  Now  prepare  the  facing  carefully  as 
follows :  Grind  the  facing  shorter  than  you  desire  by  the  thick- 
ness of  No.  34  gold  plate ;  grind  off  both  angles  left  at  the 
cervical  portion,  and  also  grind  the  cutting-edge  on  the  palatal 
side  from  pins  to  cutting-edge,  leaving  a  feather-edge  at  the 
cutting-surface ;  likewise  grind  the  cervical  portion  from  pins 
to  cervical  margin,  leaving  this  margin  also  a  feather-edge  ; 
also  remove  angles  from  pins  to  approximal  margins,  the 
object  being  to  give  a  perfectly  convex  contour  to  the  palatal 
side  of  the  facing. 


ROOT    CROWNING.  255 

After  grinding  off  the  heavy  angles  with  the  lathe,  use  disks  in 


Fig.  286. 


Fig.  287. 


FlG.'2{ 


the  engine,  and  be  sure  that  all  angles  are  removed. 
Sometimes  it  is  even  necessary  to  go  between  the  pins 
with  a  disk.  Now  take  Scotch  stone  and  make  the  sur- 
face perfectly  smooth,  edges  particularly,  or  the  gold 
cannot  be  brought  in  absolute  contact.  Three  different 
views  of  a  facing  so  prepared  are  shown  in  Fig.  287.  The 
surface  where  the  pins  are  being  the  highest  part,  the 
grinding  of  the  palatal  surface  is  done  so  as  to  fill  in 
with  twenty-carat  solder  and  give  all  the  strength  that 
would  be  obtained  if  we  ground  the  cutting-edge  off 
square,  for  when  the  tooth  is  finished  we  have  a  slightly 
beveled  surface  of  gold  at  the  cutting-edge,  the  facing 
having  only  a  feather-edge  ;  but  that  edge  is  well  pro- 
tected, so  we  get  great  strength.  We  secure,  besides,  artistic 
beauty  by  having  the  facing  exactly  the  shape  of  the  natural 
tooth  on  the  whole  labial  surface.  By  this  method  of  shaping 
the  facing  we  never  have  a  tooth  to  crack,  because  there  are  no 
angles,  and  finally  the  solder  will  flow  perfectly  around  the  cer- 
vico-labial  surface. 

Now  take  this  facing  (being  sure  that  the  palatal  surface  is 
clean)  and  back  it  with  pure  gold,  No.  34,  allowing  the  gold  to 
project  a  little  at  both  cervical  and  cutting-edges.  In  order  to 
back  this  facing  so  that  the  pure  gold  is  in  absolute  contact  with 
the  facing,  anneal  several  times,  each  time  pressing  it  in  contact 
with  the  facing  with  a  broad  instrument  like  a  plastic  spatula  No. 
20  (Fig.  288).  Never  stop  annealing  and  working  to  place 
until  the  tooth  can  be  held  in  contact  with  the  backing  at 
the  cutting-edge  and  permits  no  motion  of  gold  at  the  cervical 
margin.     The  same  with  the  approximal  surfaces.     Now  hold 


256  MECHANICAL    DENTISTRY. 

the  tooth   and   backing   between  the   thumb   and   middle  fore 
fingers  tightly,  and  with  the  point  of  a  pocket-knife  push  the 
gold  into  hard  contact  with  the  pins  all  around,  using  the  very- 
point  of  the  knife,  and  there  will  be  no  occasion  to  bend  the  pins  ; 
besides,  it  makes  a  perfect  gold  surface. 

Place  the  facing  with  its  backing  on  the  foundation,  wax  up 
with  hard  wax,  and  try  it  in  position  in  the  mouth.  If  doubt 
exists  as  to  the  correctness  of  the  position,  stay  it  well  with  hard 
wax,  then  try  again  for  position.  After  obtaining  it,  finish  wax- 
ing up  until  the  contour  is  anatomically  correct,  leaving  a 
little  margin  all  around  the  backing  so  as  to  be  perfectly  boxed 
in.  This,  is  done  just  as  in  the  case  of  the  molar,  by  making  a 
tin-foil  model  (Fig.  289)  and  bringing  the  gold  into  absolute  con- 
tact with  the  backing,  because  if  a  small  space  is  left  borax  will 


Fig.  289.  Fig.  290.  Fig.  291. 


run  through  and  crack  the  tooth.     Great  care  must  be  exercised 
with  regard  to  this  contact. 

This  cuspid  box  may  be  made  in  two  pieces,  joined  at  the 
cervico-labial  surface  the  same  as  seen  at  the  cervico-palatal 
and  cutting-edges.  When  we  bring  the  gold  across  the  cutting- 
edge,  which  has  the  gold  projecting  a  little,  not  bent  over  the 
edge,  but  projecting  in  perfect  contact,  make  the  pure  gold  go 
just  a  little  lower  than  the  cutting-edge,  so  as  to  have  a  little 
bevel  of  twenty-carat  gold,  so  slight  that  it  cannot  be  seen  (Fig. 
290).  For  exceedingly  heavy  use  leave  the  bevel  a  little  thicker, 
but  even  that  is  scarcely  noticeable.  Now  fill  in  the  junc- 
tion of  the  boxing  with  the  backing,  and  also  of  the  cervical 
margin  of  the  foundation  with  wax,  and  invest  the  same  as  for 
a  solid  crown,  allowing  the  plaster  and  marble-dust  to  come  over 
the  cervico-palatal  boxing,  etc. 


ROOT    CROWNING.  257 

To  solder  this  crown,  place  but  a  few  pieces  of  twenty-carat 
solder  and  borax  in  before  using  the  Knapp  blowpipe,  because 
we  want  the  first  gold  to  flow  perfectly  at  the  cervico-labial  sur- 
face and  so  avoid  air-bubbles,  after  which  the  course  is  clear. 
After  the  soldering  is  completed,  place  the  crown  under  a  little 
box,  so  that  it  may  cool  off  slowly  and  no  draught  can  reach  it. 
When  cold,  boil  in  dilute  sulphuric  acid.  This  gold  will  cut  down 
absolutely  in  contact  with  the  tooth,  and  when  the  cutting-edge 
is  finished  with  a  slight  bevel,  it  will  be  seen  and  understood 
what  great  strength  has  been  secured,  with,  at  the  same  time,  a 
beautiful  labial  facing  of  porcelain.  When  the  cervical  surface, 
in  fact,  the  whole  crown,  is  finished  up  in  the  thorough  and 
artistic  manner  of  which  it  is  capable,  it  becomes  a  piece  of  per- 
fection.    (See  Fig.  291.) 

A  bicuspid  is  made  exactly  the  same  as  a  cuspid,  with  the 
exception  of  the  stamp.  Make  the  stamp,  and  fill  the  cusps  with 
twenty-two-carat  solder,  then  hollow  out  the  buccal  cusp  to  fit 
the  cusp  of  the  facing,  and  place  a  very  narrow  piece  of  pure 
gold  at  the  junction  on  the  buccal  surface,  and  continue  as  in  the 
cuspid.  (See  Fig.  292.)  If  the  bicuspid  is  a  short  one,  do  not 
be  afraid  of  cracking  the  facing  ;  grind  and  make  it  exactly  as 
directed,  and  it  will  not  crack.  Notice  the  curve  in  the  bicuspid 
cut. 

For  a  bridge-tooth,  take  a  superior  right  cuspid.  Now  when 
grinding  a  tooth  to  fit  the  gum  we  necessarily  expose  the  small 
porosities  in  the  body  of  the  tooth,  which  always  have  a  tend- 
ency to  lodge  food,  thus  producing  an  offensive  breath.  To 
correct  this  defect,  shape  up  this  cuspid  exactly  the  same  as  if 
we  were  making  a  crown,  and  back  it 
up  the  same  way.  Now  flow  wax  over 
the  whole  surface,  and  regulate  the  thick- 
ness of  the  wax  according  to  the  re- 
quired fullness  of  the  tooth,  boxing  in 
with  pure  gold  the  height  of  the  wax 
and  restoring  the  shape  of  the  lost 
tooth  ;   then    invest   to   the  top  of  the 

boxing,  and  after  the  proper  steps  of  investing  fill  in  with  gold. 
Here  there  are  two  great  points  to  observe.     First,  this  gold 
17 


258  MECHANICAL    DENTISTRY. 

can  be  finished  absolutely  smooth,  so  that  nothing  can  collect 
in  the  way  of  food,  hence  nothing  but  perfect  cleanliness  can 
exist.  Secondly,  any  amount  of  absorption  of  gum  can  be 
counteracted  by  building  out  with  gold  exactly  the  amount  of 
absorption.  This  will  give  the  tooth  a  natural  position,  a  per- 
fectly smooth  palatal  surface,  and  restore  the  lip  to  its  normal 
(or,  in  case  of  a  cuspid,  almost  normal)  expression. 

Dr.  Low's  Method. — The  following  description  of  an 
original  method  of  crown  replacement  was  prepared  by  Dr.  J. 
E.  Low,  of  Chicago,  111.  The  inventor  claims  exceptional  advan- 
tages for  his  method,  and  has  also  presented  them  to  the  profes- 
sion in  connection  with  bridge-work,  which  article  we  also 
introduce  under  its  appropriate  head  in  another  place. 

"  This  crown  is  the  result  of  an  effort  to  overcome  the  ma^y 
objectionable  features  to  be  found  in  other  crowns  in  use  at  the 
present  day. 

"  Having  had  an  extensive  experience  in  crown-work,  with  a 
thorough  knowledge  of  all  crowns  in  use,  and  with  the  many 
letters  now  before  me  from  various  parts  of  the  country,  con- 
taining testimonials  to  this  effect,  I  think  I  can  justly  claim  that 
this  crown  is  nearer  to  perfection  than  any  other  before  pre- 
sented to  the  notice  of  the  dental  profession.  I  am  aware  that 
the  average  dentist  does  not  differ  from  the  rest  of  humanity  at 
large  in  the  matter  of  changing  their  mode  of  operating,  and 
when  any  new  improvement  is  presented  to  them,  they  at  once 
begin  to  see  what  objection  they  can  raise  against  it,  instead  of 
recognizing  its  good  qualities  and  advantages  over  others.  As 
I  have  had  a  good  opportunity  to  know  most  of  the  objections 
raised  against  the  crown  in  question,  I  think  it  best  here  to 
mention  those  of  importance  and  show  how  incorrectly  they 
have  been  drawn. 

"  Now,  I  do  not  wish  the  reader  to  think  for  a  moment  that  I 
object  to  criticism,  providing  it  is  just,  for  this  would  assist  me 
in  regulating  what  imperfections  there  might  be,  to  the  benefit 
of  all.  One  of  the  most  common  objections  raised  by  those 
who  have  never  used  the  crown,  is  that  the  instruments  cut 
away  too  much  tooth  substance  in  preparing  the  root,  and  the 
walls  of  the  tooth  are  thereby  weakened. 


ROOT    CROWNING. 


259 


"  Then,  again,  some  claim  that  it  is  necessary  to  have  a  band 
around  the  tooth  to  prevent  it  from  splitting.  The  other  objec- 
tions are  not  of  enough  importance  to  notice.  I  will  now 
proceed  to  set  a  crown  by  this  method,  and  if,  in  so  doing,  I  am 

Fig.  293. 


clear  and   comprehensive,  I  think  all   will   agree   with   me    in 
saying  these  objections  are  not  well  founded. 

"  By  carefully  looking  over  the  case  of  instruments  represented 
in  Fig.  293,  you  will  find  there  are  seven  in  number,  instrument 
No.  I  being  the  smallest.     This  instrument  can  be  used  in  more 


26o 


MECHANICAL    DENTISTRY. 


cases  to  advantage  than  any  other.  Ahnost  all  the  laterals,  and 
nearly  all  the  bicuspids,  as  well  as  all  badly  decayed  molars,  when 
so  decayed  that  gold  crowns  cannot  be  used,  and,  in  fact,  any 
tooth  that  is  generally  set  down  as  beyond  restoration,  can  be 
crowned  successfully  with  this  instrument. 

"  We  now  have  before  us,  Fig.  294,  a  central  incisor  badly 
decayed.  The  first  step  to  be  taken  to  crown  this  root 
Fig.  294.  with  a  strong  and  serviceable  crown,  is  to  cut  or  grind 
even  with  the  gum  what  tooth  substance  remains.  We 
start  off  with  the  supposition  that  the  root  is  in  a  healthy 
condition  ;  if  not,  it  must  first  be  treated,  and  made  so, 
as  this  is  the  first  consideration  in  the  final  result  of  a 
successful  operation.  The  next  step  is  to  select  the 
instrument  in  accordance  with  the  size  of  the  opening 
in  the  root  to  be  crowned.  The  larger  the  opening  in  the  root, 
the  larger  the  inside  or  center  cutters  must  be,  and  the  narrower 
the  cutters  that  bevel  and  prepare  the  end  of  the  root.  The  reason 
of  this  is  that  the  space  is  nearly  all  taken  up  by  the  inside  cutters, 
in  order  to  reach  and  cut  away  the  decayed  tooth  substance,  and 
prepare  the  root  to  properly  receive  the  step-plug  with  bevel  cap, 
which  covers  the  end. 

"  We  have  seven  sizes  of  instruments  to  select  from,  and  when 
properly  selected,  no  tooth  substance  that  ought  not  to  be 
removed  will  be,  cutting  as  they  do  the  least  where  the  tooth  is 
smallest,  or,  in  other  words,  cutting  the  opening  in  the  tooth  in 
the  same  shape  as  the  root — tapering. 

"  These  cutters  leave  the  root  in  the  shape  of  Fig.  295  with 
graded  steps.  We  next  select  the  graded 
step-plug  as  seen  in  Fig.  296,  the  same 
number  as  the  instrument,  which  will 
perfectly  fit  the  opening,  and  cover  the 
end  in  a  beveled  saucer  shape,  and  by 
its  attachment  when  cemented  makes  a 
combined  union  of  strength,  unequaled 
by  any  other  crown,  and  thus  it  is  made 
impossible  for  the  root  to  split.  In  Fig.  297  we  have  the  step- 
plug  placed  in  position. 

"  After  placing  the  plug  in  position,  an  articulation  of  wax,  and 


F1G.295 


ROOT    CROWNING. 


261 


an  impression  of  the  space  to  be  supplied,  and  a  few  adjoin- 
ing teeth,  are  taken  in  plaster-of-Paris.  Before  taking  the 
impression,  be  careful  that  the  pin  which  extends  from  the  cap 
of  step-plug  for  the  purpose  of  removing  is  free  from  all  rough- 
ness (a  roughness  that  is  sometimes  left  in  the  cutting  of  the  plug), 
as  this  is  liable  to  break  the  plaster  when  removing  the  impres- 
sion from  the  mouth.  I  generally  file  the  step-plug  on  a  slant 
from  the  labial  side  to  the  center,  so  that  there  will  be  no  mis- 
take in  replacing  the  step-plug  into  its  proper  place  in  the  im- 
pression. After  placing  the  plug  back  in  the  impression,  if 
necessary,  take  a  thin,  heated  spatula,  and  stick  the  plug  fast  with 
a  little  hard  wax  on  the   outer  edge,  so  that  it   may  not  be   dis- 


FlG. 


Fig.  300. 


Fir,.  299. 


turbed  in  pouring.  Be  careful  not  to  get  any  wax  on  the  part  of 
the  plug  where  you  do  not  want  solder  to  flow  in.  Now  varnish 
the  cast  in  the  usual  way,  but  do  not  touch  the  plug  with  the 
varnish.  Next,  pour  with  plaster  and  sand,  asbestos  or  pulverized 
pumice  stone,  any  one  of  which  will  do.  After  the  plaster  is 
thoroughly  hardened,  carefully  cut  it  away  in  the  usual  manner. 
Place  the  articulation  in  the  articulator,  and  pour  in  the  usual 
way.  The  tooth  is  selected,  and  we  proceed  to  back  the  same  in 
the  following  manner:  First,  grind  and  fit  the  tooth  to  the  cast 
and  cap  to  suit  you  ;  then  cover  the  entire  inner  surface  with 
thin  platinum,  the  thinner  the  better.  Burnish  close  to  the  sur- 
face of  the  tooth.  Then  use  28-gauge  platinum  for  a  backing 
down  to  where  the  tooth  is  ground  out  to  fit  the  step-plug,  and 


262  MECHANICAL    DENTISTRY. 

bend  the  pins  down  to  hold  the  two  pieces  of  platinum  tight  to 
the  tooth.  We  now  have  Fig.  298  representing  the  tooth  as  it 
appears  backed  ready  to  place  in  position.  Next  place  the  tooth 
in  position  in  the  cast,  cover  with  plaster  and  sand,  and  solder 
with  gold  coin.  After  finishing  and'polishing,  the  crown  is  ready 
for  adjustment.  Moisten  the  step-plug  and  cap  with  cement,  and 
with  the  little  roter,seen  in  Fig.  299  or  in  the  case,  gently  press  the 
crown  up  in  position,  and  we  have  the  crown  completed  as  seen 
in  Fig.  300. 

"  Should  you  desire  a  cheap  crown,  you  can  solder  with  block 
tin.  After  experimenting  with  various  metals,  I  have  succeeded 
in  making  a  step-plug  or  tip  of  platinum  and  nickel  that  is  as 
strong  as  steel  and  cannot  be  melted.  In  the  above  description 
I  have  given  my  way  of  making  the  crown.  This  given  in  de- 
tail seems  like  a  long,  tedious  method,  but  it  is  very  short ;  and 
as  I  always  keep  a  laboratory  man,  but  very  few  minutes  of  my 
time  are  consumed  in  making  and  setting  a  crown,  not  ex- 
ceeding twenty  minutes  in  any  case,  as  I  only  prepare  the  root, 
take  an  articulation  and  impression,  and,  with  the  shade  of  the 
tooth,  hand  in  to  the  laboratory  man.  When  my  patient  returns, 
providing  the  crown  is  not  made  while  I  am  doing  some  other 
work  for  the  same  party,  it  takes  me  from  ten  to  fifteen  minutes, 
counting  the  setting  of  the  cement,  to  adjust  the  crown. 

"  The  above  is  my  manner  of  setting  the  crown  in  order  to 
save  time  at  the  chair.  Should  I  perfect  the  crown  myself,  I 
should  take  a  shorter  way,  viz. :  after  preparing  the  root  with 
the  instrument  and  placing  the  step-plug  in  position,  my  tooth 
is  selected,  ground,  and  arranged  in  the  mouth,  after  which  I 
back  the  tooth  as  before  described ;  then  soften  a  little  piece  of 
hard  wax,  made  of  resin,  gutta-percha,  and  beeswax.  I  warm 
and  stick  a  small  amount  of  this  to  the  backing  of  the  tooth, 
place  the  tooth  in  position  in  the  mouth,  perfectly  embedding 
the  top  of  the  step-plug  in  the  wax.  Great  care  must  be  exer- 
cised here  to  have  the  tooth  in  the  position  desired,  in  pressing 
the  tooth  and  wax  against  the  plug.  I  next  carefully  remove 
the  wax  and  tooth,  and  with  pliers  remove  the  step-plug  and 
place  in  the  impression  just  made.  Then  with  a  heated  spatula 
stick  the  tip  and  wax  together;  pour  in  the  usual  way,  and  in  a 


ROOT   CROWNING.  263 

few  minutes  it  is  ready  to  solder.  In  this  way  a  crown  can  be 
set  easily  in  one  hour's  time. 

"  If  you  wish  to  crown  a  bicuspid  or  molar  tooth,  your  first 
step  is  to  grind  what  little  tooth  substance  there  may  be  down 
even  with  the  margin  of  the  gum  and  then  use  your  drill.  In 
drilling,  instead  of  following  the  nerve  cavity  direct,  which 
would  leave  the  instrument  a  little  diagonal,  hold  the  instrument 
perpendicular.  This  leaves  the  upper  portion  of  drill  to  the 
outer  wall  of  the  root,  and  brings  the  lower  portion  of  drill  to 
the  inner  side  of  the  root.  There  would  be  danger  of  punctur- 
ing the  wall  of  the  root,  should  you  continue  going  deep  enough, 
but  there  is  no  need  of  going  to  such  a  depth.  Then  take  the 
No.  I  cutter,  which  will  invariably  be  the  instrument  to  operate 
upon  all  the  bicuspid  and  molar  root  canals,  and  after  cutting  to 
the  depth  desired,  the  root  is  ready  for  the  introduction  of  the 
first  step-plug  of  same  size.  We  now  drill  one  other  root  in  the 
same  manner,  and,  after  placing  the  step-plugs  in  position,  take 
an  articulation  and  impression,  remove  the  plugs,  and  place  in  the 
impression  ;  pour  and  separate,  and  place  in  the  articulator  as 
described  before.  We  now  have  an  exact  impression  of  the  root 
to  be  crowned,  with  a  kw  adjoining  teeth. 

"  Next  take  a  thin  piece  of  platinum  and  make  two  perforations 
for  the  pins  on  the  ends  of  the  step-plugs  to  enter  ;  press  the 
platinum  down  over  the  root  and  burnish  close  to  it;  then  re- 
move the  same  and  trim  by  the  marks  made  in  burnishing  to  the 
exact  shape  of  the  root.  Place  the  platinum  on  the  root  again, 
and  we  are  ready  to  select  our  tooth.  This  should  be  made  the 
same  as  is  used  for  bridge-work,  with  gold  cusps,  so  no  breakage 
can  possibly  occur.  Now  place  the  tooth  in  position  in  the 
articulator,  holding  it  in  place  with  wax.  Encase  in  plaster  and 
sand,  fill  in  and  solder  up  with  gold  coin  ;  or,  if  you  choose, 
block  tin  can  be  used.  After  polishing  and  burnishing,  you  have 
a  strong,  durable  crown,  only  equaled  by  the  natural  tooth,  ready 
to  be  adjusted. 

"  The  setting  of  a  bicuspid  is  similar  to  that  of  a  molar.  In 
this  operation  we  seldom  use  but  one  step-plug. 

"In  Fig.  301  we  have  the  root  cut  ready  to  receive  the  step- 
plug. 


264 


MECHANICAL    DENTISTRY. 


"  In  Fig.  302  we  have  the  step-plug  with  the  platinum  attached, 
which  covers  the  entire  tooth  surface. 

"  In  Fig.  303  it  will  be  seen  that  the  cap  of  the  step-plug  goes 
below  the  surface  of  the  tooth,  leaving  tooth  substance  all  the 
way  around ;  but  the  platinum  that  is  soldered  to  the  step-plug 
rests  on  the  tooth  surface. 

"  In  Fig.  304  we  see  the  crown  ready  for  adjustment. 

"  F'g-  305  is  the  tooth  after  it  has  been  adjusted 

"  These  plugs  can  be  used  to  great  advantage  in  varied  dental 
operations.  There  is  nothing  equal  to, them  for  restoring  broken 
and  decrepit  teeth  to  their  original  usefulness.  I  use  them  ex- 
clusively in  bridge-work.  They  make  a  firmer,  stronger,  and 
more  durable  groundwork  for  bridging  than  any  other  method 
I  have  ever  discovered.  In  badly-decayed  molars,  where  there 
is  not  sufficient  tooth  substance  to  hold  a  gold  crown  for  bridge. 


Fig.  301.        Fig.  302.        Fig.  303.        Fig.  304.        Fig.  305. 


I  always  place  one  of  these  plugs  in  the  root,  which  makes  a 
solid  foundation.  If  the  pin  on  the  end  of  the  plug  for  remov- 
ing is  not  long  enough,  it  can  be  very  readily  lengthened  by 
soldering  a  piece  to  it  without  danger  of  injury  or  melting  the 
same.  The  plugs  are  made  of  a  perfectly  non-corrosive  metal, 
although  the  color  might  indicate  otherwise.  They  are  strong 
as  steel,  and  cannot  be  melted  by  heat  from  an  ordinary  blow- 
pipe." 

Dr.  Biittner's  Method.— Dr.  H.  W.  F.  Buttner,  of  New  York, 
to  secure  the  attachment  of  a  porcelain  crown  to  the  root,  has 
made  available  the  mechanical  device  known  as  a  mortise-joint, 
the  root  being  shaped  by  trephining  to  the  form  of  a  tenon,  a 
gold  band  or  ferrule  forming  the  mortise.  The  following  is  his 
description  of  the  process  : — 

"  In  my  method  of  setting  artificial  crowns,  I  claim  simplicity 


ROOT    CROWNING.  265 

of  construction,  firmness,  durability,  and  arrest  of  decay  of  the 
root  (Fig.  306).  From  the  following  description  of 
my  method  it  would  seem  that  a  failure  would  be  ^^^-  3o6. 
almost  impossible.  To  protect  the  end  of  the  root 
from  decay,  and  to  obtain  a  strong  hold  for  an  arti- 
ficial porcelain  crown,  a  gold  band,  properly  applied, 
must  be  of  the  greatest  benefit.  I  am  aware  of  the 
fact  that  gold  bands  have  been  applied,  but  I  am 
convinced  that  their  adaptation  after  any  of  the  old 
methods  is  defective.  What  I  claim  in  my  method  is 
the  preparation  of  the  neck  of  the.  root  by  a  set  of  instruments 
especially  constructed  for  that  purpose.  These  instruments 
enable  the  operator  to  obtain  as  nearly  perfect  adaptation  be- 
tween the  gold  band  and  the  root  of  the  tooth  as  can  possibly 
be  made.  With  reference  to  the  upper  centrals,  laterals,  and 
canines,  as  well  as  the  corresponding  lower  teeth  and  bicuspids, 
there  can  be  nothing  more  favorable  than  the  application  of  this 
method.  It  is  true  that  this  process  cannot  be  applied  with  the 
same  advantage  to  the  upper  bicuspids  or  any  of  the  molars, 
but  I  hope  in  time,  if  I  am  in  any  way  supported  by  the  pro- 
fession, to  solve  that  problem.  I  believe  I  will  succeed  in  con- 
structing a  set  of  instruments  which  will  prepare  a  root  the 
pulp  of  which  is  alive,  and  may,  if  healthy,  be  readily  kept  so. 
But  as  this  set  of  instruments  is  not  quite  completed,  I  will 
abstain  from  its  description,  and  only  allude  to  the  setting  of 
crowns  which  require  the  devitalization  of  the  pulp,  unless  this 
organ  has  previously  died.  With  these  instruments  a  circular 
shoulder  is  turned  on  the  neck  of  the  root. 

"  The  alteration  of  the  neck  of  the  root  from  an  irregular 
cone  to  a  cylindrical  form  enables  us  to  adapt  a  corresponding 
ring  or  cap.  Such  a  cap,  when  fitting  accurately  around  as  well 
as  upon  the  end  of  the  root  prepared  by  these  instruments,  forms 
an  air-tight  joint,  and  consequently  protects  it  from  decay,  at 
the  same  time  giving  the  porcelain  crown,  when  attached,  a 
firmness  which  heretofore  has  never  been  obtained.  The  set  of 
instruments  by  which  the  neck  of  the  root  is  prepared  consists 
of  drills,  reamers,  and  trephines.  The  drills  (Fig.  307)  are  used 
to  enlarge  the  root-canal  for  the  guidance  of  the  reamer  or  facing 


266 


MECHANICAL    DENTISTRY. 


instrument  and  trephine.  The  reamers  (Fig.  308)  cut  the  surface 
of  the  root  down  as  far  as  necessary.  They  produce  a  perfectly 
level  surface  and  have  a  center-pin,  which  corresponds  with  the 
hole  made  by  the  drill  in  the  center  of  the  root,  and  acts  as  a 
guide.  The  trephine  (Fig.  309)  has  also  a  center-pin,  and  is 
used  to  make  the  root  cylindrical  below  the  free  margin  of  the 
gum.  A  set  of  these  instruments  includes  different  sizes  of 
drills,  with  reamers  and  trephines  corresponding  in  size  adapted 
to  various  diameters  of  roots. 

"The  ferrules  or  caps  (Fig.  310)  to  fit  roots  which  have  been 
prepared  by  the  above  instruments  are  of  gold,  made  by  steel 
dies.     They  correspond  exactly  with  the  trephine  in  diameter 


Fig.     Fig.        Fig. 
307.     308.       309. 


Fig.  311. 


and  depth,  with  allowance  for  sufficient  expansion  of  the  gold 
when  forced  on  to  the  shoulder  of  the  root,  whereby  a  most 
perfect  joint  between  cap  and  root  is  obtained.  They  have  a 
stout  central  pivot  which  fits  the  hole  in  the  root  and  gives 
increased  strength  and  firmness. 

"  The  pulp-canal  is  enlarged  with  one  of  the  drills  selected 
with  reference  to  the  size  of  the  root.  A  reamer  corresponding 
in  size  is  used  with  the  dental  engine  to  cut  the  root  down  to  a 
perfect  level.  The  trephine  is  applied  in  the  same  manner  to 
give  a    cylindrical  form  to   it,   thus    completing  the    shoulder 

(Fig.  31  0- 

"  A  steel  wire  corresponding  in  diameter  with  the  drill  which 


ROOT    CROWNING.  26/ 

has  been  employed  is  now  introduced  into  the  root,  projecting 
about  half  an  inch.  It  serves  to  indicate  the  exact  direction  of 
the  root-canal.  An  impression-cup  is  selected  with  an  open- 
ing opposite  the  missing  tooth  to  take  an  impression  of  the 
root  and  adjoining  parts.  The  object  of  the  opening  is  to  give 
free  transmission  to  the  wire  in  the  root-canal.  The  wire  pro- 
truding through  the  cup  and  impression-material  is  drawn  out 
carefully  before  the  removal  of  the  impression-cup,  which  is 
then  removed  and  the  wire  placed  in  its  proper  position  in  the 
impression.  A  set  of  brass  root-models  (Fig.  312)  correspond- 
ing in  size  with  the  instruments  accompany  them  ;  one  of  these, 
bearing  the  same  number  as  the  instrument  with  which  the  root 
has  been  prepared,  is  now  placed  on  the  wire  in  the  impression, 
and  serves  to  represent  the  prepared  end  of  the  root  on  the 
model.     The  impression  is  now  ready  to  be  filled  with  plaster. 

After  the    cast    is  obtained,  we  find  the   root-  tt.  t7 

'  Fig.  312.    Fig.  313. 

model  imbedded  in  the  plaster  and  the  wire  in 
its  center-hole.  The  wire  is  removed  and 
the  plaster  cut  from  around  the  root-model  to 
the  depth  of  the  gold  cap,  which  is  ready  to  be 
placed  upon  it.  A  plain  porcelain  tooth  (Fig.  313),  as  used  in 
plate-work,  is  ground  hollow  on  the  inner  surface  to  cover  the 
outer  front  wall  of  the  cap,  thus  hiding  the  gold.  Thin  platinum 
backing  is  adapted  to  the  tooth,  which  is  then  ready  to  be 
placed  in  position  on  the  model  over  the  gold  cap,  and  fastened 
thereon  with  hard  wax.  The  united  parts  are  removed  care- 
fully from  the  model,  invested  in  sand  and  plaster,  and  soldered. 
After  polishing,  the  cap  is  ready  to  be  forced  upon  the  root  by 
placing  a  piece  of  wood  on  the  cutting-edge  of  the  tooth 
and  driving  it  home  with  a  mallet," 

Dr.  Matteson's  System. — The  following  process  of  forming 
and  attaching  a  porcelain-faced  crown,  taken  from  the  OdoJito- 
graphic  Journal,  is  the  device  of  Dr.  A.  E.  Matteson,  of  Chicago, 
111.  The  method  of  constructing  a  shell  in  conformity  with  the 
general  configuration  of  the  natural  crown  is  unique  and  original, 
while  the  facility  with  which  it  can  be  so  shaped,  the  accuracy 
and  security  of  its  adjustment  to  the  root,  and  the  ready  manner 
in  which  the  porcelain  face  may  be  replaced  in  case  of  accident. 


268 


MECHANICAL    DENTISTRY. 


are  points  of  excellence  that  entitle  the  method  to  rank  among 
the  higher  forms  of  substitution.  The  several  appliances  used 
are  exhibited  in  Fig.  314.  Concerning  the  process,  the  inventor 
says : — 

"  The  gold-and-platinum  plate  gives  the  greatest  strength 
without  an  excess  of  material,  permitting  the  use  of  a  higher 
grade  of  solder  than  could  be  employed  were  gold  alone  used, 
without  the  consequent  danger  of  melting  the  shell ;  and  being 

Fig.  314. 


of  uniform  thickness,  its  thorough  adaptation  to  the  end  of  the 
root  is  rendered  a  matter  of  comparative  ease  and  certainty.  It 
also  permits  the  use  of  amalgam,  the  strongest  cement  we  have, 
for  anchoring  the  crown  without  danger  of  injury  to  the  gold. 
I  will  say,  however,  to  those  who  are  opposed  to  the  use  of 
amalgam,  that  gutta-percha,  or  any  of  the  cements,  can  be  sub- 
stituted, and  with  as  good  results  as  in  any  other  position  in  the 
mouth. 


ROOT    CROWNING.  269 

"  The  opening  in  the  front  of  the  shell  gives  an  opportunity  to 
see  that  the  filling  is  properly  introduced,  thoroughly  condensed, 
and  is  not  guesswork. 

"  The  porcelain  front  is  not  dependent  upon  a  few  small  pins 
for  support,  but  upon  the  dovetailed  slot,  further  supported  by 
the  edges  of  the  shell,  which  entirely  surround  it;  and  in  case 
of  fracture,  a  new  front  can  be  easily  inserted  without  removing 
the  shell. 

"  Of  no  small  importance  is  the  ease  with  which  this  crown 
can  be  made.  Even  in  the  hands  of  those  unaccustomed  to 
metal  work,  good  results  may  be  obtained. 

"  The  forceps,  with  a  set  of  eleven  dies  and  counter-dies,  are 
all  that  are  required  in  addition  to  the  instruments  usually  in 
possession  of  a  dentist  in  practice. 

"  The  root  upon  which  the  crown  is  to  be  mounted  should  be 
placed  in  a  healthy  condition,  with  the  nerve-canal  filled  at  the 
apex,  the  end  ground  off  bdozv  the  free  margin  of  the  gum  in 
front,  and  within  an  eighth  of  an  inch  of  the  gum  on  the  inner 
or  lingual  surface,  the  end  of  the  root  countersunk,  and  the 
nerve-canal  enlarged  sufficiently  to  receive  aplatinum  wire — No. 
18  or  20,  standard  plate  gauge — with  a  screw-thread  cut  thereon. 
This  should  fit  tightly  enough  to  take  firm  hold.  Further  en- 
large one-half  the  length  of  the  nerve-canal  with  a  cone-shaped 
bur,  with  its  base  toward  the  apex,  as  represented  in  the  accom- 
panying cut.  No.  I. 

"  Previous  to  grinding  the  end  of  the  root  bcloiv  the  gum  in 
front,  take  a  measurement  of  the  circumference  of  the  root  at 
the  margin  of  the  gum  with  fine  binding  wire.  Cut  across  an 
intersection  and  carefully  remove  the  wire  ring  thus  formed, 
without  changing  its  shape.  Take  an  impression  of  its  form 
by  placing  it  between  a  sheet  of  writing  paper  and  a  smooth 
surface,  and  by  rubbing  the  end  of  a  finger  thereon  the  outline 
will  appear.  This  is  the  outline  of  the  end  of  the  root ;  from 
this  cut  a  pattern. 

"  Select  a  die  similar  in  shape  to  the  tooth  you  wish  to  repro- 
duce. Make  a  pattern  of  the  shell  by  pressing  between  the 
dies  a  piece  of  thin  copper  or  pattern  tin,  leaving  an  opening  in 
front,  with  a  band  extending  around  in  front,  as  represented  in 


270  MECHANICAL    DENTISTRY. 

No.  3,  the  cut  being  on  a  line  with  the  edge  on  one  side.  Re- 
move this  pattern  and  press  into  as  plain  a  surface  as  possible. 

"  Cut  the  gold-and-platinum  plate  to  pattern,  making  it  wider 
or  narrower,  as  the  wire  measurement  of  the  end  of  the  root 
compared  with  the  pattern  indicates.  Anneal  and  place  the 
plate  in  the  same  position  between  the  dies  as  that  previously  oc- 
cupied by  the  pattern  ;  and  press  into  form,  remove,  bring  the 
edges  together  without  lapping,  and  solder  with  pure  gold.  The 
shell  may  be  made  longer  or  shorter,  wider  or  narrower,  than 
the  die  upon  which  it  was  made,  as  the  case  demands. 

"  To  fit  the  shell  to  the  root,  trim  the  root  end  of  the  shell 
until  it  occupies  its  proper  position  and  the  articulation  is  cor- 
rect, which  is  determined  by  the  patient  closing  the  teeth.  The 
corners  at  the  cutting  edge  and  sides  should  be  cut,  and  the 
edges  brought  together  without  lapping,  and  also  soldered  with 
pure  gold. 

"  Now,  from  platinum  plate  No.  30,  cut  the  ring.  No.  4,  to  the 
paper  pattern.  This  forms  the  shoulder  within  the  shell.  Place 
the  shell  in  position  on  the  root  (the  teeth  closed),  insert  the  ring, 
which  should  rest  upon  the  end  of  the  root  midway  the  width  of 
the  band  in  front,  and  should  fit  the  shell  tight  enough  so  that  both 
can  be  removed  without  changing  their  relative  positions.  Remove 
from  the  root,  and  with  a  fine  camel's-hair  brush  apply  finely 
ground  borax  dissolved  in  water.  At  the  junction  of  the  two 
pieces,  place  a  small  piece  of  20  k.  solder  on  the  inner  surface,  i.  e., 
toward  the  cutting  edge  of  the  shell,  to  prevent  an  excess  of 
solder  flowing  between  the  shoulder  and  the  end  of  the  root  upon 
which  it  will  rest.  Flow  the  solder,  which  should  merely  tack 
the  ring  in  place  at  the  front.  Try  upon  the  root  to  make  sure 
of  its  being  correct ;  remove,  and  complete  the  soldering.  The 
shell  may  be  strengthened  by  flowing  inside,  a  lower  grade  of 
solder  than  previously  used,  at  such  places  as  desired. 

"  Select  a  plain  rubber  tooth  and  fit  to  the  opening  in  the  shell 
(which  may  be  removed  for  the  purpose),  and  with  corundum- 
wheel  and  disk  grind  a  dovetailed  slot  in  the  back  (see  No.  5), 
running  lengthwise,  and  sufficiently  deep  to  permit  the  platinum 
screw  to  extend  two-thirds  the  length  of  the  crown  without  inter- 
ference. 


ROOT    CROWNING.  27 1 

"  To  anchor  the  crown  to  the  root,  place  the  shell  in  position, 
apply  the  rubber  dam  over  it  and  the  adjoining  teeth,  turning  the 
edges  well  under  the  gum.  Remove  the  shell  (the  dam  will  re- 
main in  position),  dry  the  nerve-canal,  insert  the  wire-screw,  cut 
it  off  the  required  length,  and  with  amalgam  mixed  hard  fill 
around  the  screw  in  the  root  (the  end  of  the  screw  should  be 
bent  against  the  inner  wall  of  the  shell  when  the  teeth  are  closed, 
so  as  to  fall  into  the  dovetailed  slot  in  the  porcelain  front  when 
that  is  inserted).  Continue  the  amalgam  filling  through  the 
opening  in  the  front  of  the  shell  around  the  screw  and  over  the 
shoulder,  as  represented  in  No.  i  ;  and  with  oxyphosphate 
cement,  complete  by  filling  around  the  wire  and  in  the  slot  of  the 
front,  which  is  then  inserted  and  pressed  into  position  by  the 
thumb  and  finger,  the  excess  escaping  at  the  edges.  Burnish  the 
edges  of  the  shell  around  the  neck  of  the  root  and  porcelain 
front.  Instruct  the  patient  not  to  disturb  it  for  from  four  to  six 
hours. 

"  In  conclusion,  I  will  offer  some  suggestions.  The  dies 
are  fitted  to  the  forceps  with  the  cutting  edges  of  the  teeth 
turned  toward  the  handle.  Be  careful  that  the  dies  and  counter - 
dies  do  not  get  mixed.-  Preserve  the  pattern  of  each  die  with 
which  it  should  be  left,  as  it  will  save  valuble  time.  Apply  the 
flux  (borax)  only  where  you  wish  the  solder  to  flow,  and  cut  the 
solder  in  small  pieces,  using  only  sufficient  to  accomplish  its 
purpose. 

"Amalgam  may  be  made  to  set  more  quickly  by  incorporat- 
ing gold  with  the  mercury,  say  5  per  cent.  Foil  scraps  are  ex- 
cellent. 

"  In  case  of  fracture  of  the  porcelain  front,  remove  the  pieces 
and  fit  in  another,  without  removing  the  shell  from  the  root. 
Cement  in  as  before. 

"  The  cut  represents  the  forceps  one-half  size.  They  are  one- 
half  nickel-plated.  The  dies  are  full  size,  nickel-plated,  and  are 
interchangeable  in  the  screw  sockets. 

"The  gold-and-platina  plate  is  made  by  sweating  pure  gold 
upon  a  plate  of  equal  thickness  of  platinum  and  rolling  to  the 
desired  thickness  (No.  32,  plate  gauge),  and  can  be  obtained  at 
the  dental  depots." 


2/2  MECHANICAL    DENTISTRY. 

THE    ALL-GOLD    CROWN    OR    CAP. 

In  the  construction  of  the  all-gold  crown,  the  sides  of  the 
natural  crown  and  neck  of  the  tooth  are  brought  down  to — or  a 
little  smaller  than — the  size  of  the  root.  This  is  best  accom- 
plished by  the  use  of  diamond  disks  and  small  corundum-stones 
on  the  dental  engine.  From  the  occluding  surface,  if  any  of  it 
remains,  a  sufficient  amount  should  be  ground  away,  and  the 
edges  slightly  rounded,  to  allow  the  introduction  of  the  gold 
cusps.  The  measurement  and  making  of  the  band  is  the  same 
as  described  in  connection  with  the  Richmond  collar  crown  (see 
page  227),  excepting  in  the  width  of  the  ferrule.  This  should  ex- 
tend from  the  root,  below  the  gum-margin,  to  within  a  line  of  the 
occlusion  with  the  antagonizing  teeth.  After  soldering  and 
adjusting,  the  band  should  be  shaped  and  contoured  with 
burnishers  and  suitable  pliers,  the  smooth,  round-nosed,  an- 
swers very  nicely.  The  surface  of  the  band  to  which  the 
cusps  are  to  be  attached  should  then' be  brought  down  perfectly 
smooth  and  flat  with  a  fine  file  ;  readjusted  carefully  to  the  root, 
to  make  sure  that  it  has  not  been  so  distorted  by  the  different 
manipulations  that  it  will  not  pass  readily  to  place  and  fit  the 
root  perfectly  at  every  point.  Finding  all  correct,  the  next  step 
is  making  the  cusp. 

A  number  of  methods  have  been  put  forward  for  making  gold 
cusps.  The  two  that  have  proven  most  satisfactory  are  the  use  of 
the  die,  such  as  described  in  connection  with  the  Knapp-system 
of  making  crowns,  and  by  means  of  the  die  plate  as  described 
by  Dr.  E.  T.  Starr,  of  Philadelphia,  in  the  Dental  Cosmos,  as 
follows  : — 

"  In  the  construction  of  metal  cap-crowns  to  cover  natural 
teeth  or  roots  there  are  many  methods  which  result  in  good 
work,  but  in  most  cases  the  caps  do  not  articulate  as  well  as 
they  might,  for  the  reason  that  means  for  embossing  the  bicus- 
pid and  molar  cusps  are  not  at  hand,  or  available  within  the 
short  time  at  the  disposal  of  either  the  patient  or  the  dentist. 
With  the  object  of  providing  an  easy  and  quick  way  of  working 
under  such  circumstances,  I  have  made  a  single  plate.  Fig.  315, 
in  which  are  four  groups  of  intaglio  dies  representing  with  dis- 


ROOT    CROWNING. 


^/i 


tinctive  correctness  the  peculiar  cusps  of  the  upper  and  lower 
right  and  left  bicuspids  and  molars.  These  are  indicated  by 
the  Hillischer  notation,  so  that  each  form  may  be  easily  identified 
in  practice. 

"The  hubs  A  B,  Fig.  316,  are  of  the  sizes  shown,  and  are 
made  of  an  alloy  composed  of  tin  one  part,  lead  four  parts, 
melted  together.  The  mold  C  should  be  warmed,  the  melted 
alloy  poured  in  every  hole,  and  the  overflow  wiped  off  just  before 

Fig.  315. 


the  metal  stiffens.  This  will  make  the  butts  of  the  hubs  smooth 
and  flat.  After  a  minute  or  two  the  mold  may  be  reversed,  the 
hubs  shaken  out,  and  the  casting  process  continued  until  a  con- 
siderable number  of  hubs  shall  have  been  cast. 

"  In  Fig.  317  a  molar  hub  is  shown  in  place  on  a  piece  of  No. 
32  gold  plate,  which  lies  over  the  upper  right  first  molar  die. 
A  succession  of  blows  on  the  hub,  with  a  four-pound  smooth- 
faced hammer,  will  drive  the  plate  into  the  die,  and  at  the  same 
time  spread  the  hub-metal  from  the  center  to  its  circumference 
18 


274 


MECHANICAL    DENTISTRY, 


in  such  a  manner  that  the  plate  will  be  perfectly  struck-up  with 
the  least  possible  risk  of  being  cracked.  The  flattened  hub  is 
seen  in  Fig.  318,  which  also  shows  at  D  the   obverse  of  the 

Fk;.  316. 


struck-up  hub,  and  at  E  the  cameo  of  the  struck-up  plate  having 
every  cusp  and  depression  of  6.  Fig.  319  sharply  defined. 

"  The  counter-die  plate,  Fig.  315,  is  made  of  a  very  hard  cast 
metal,  which  will  admit  of  the  striking  up  of  many  crown-plates 


Fig.  317. 


Ria^^T 


by  the  means  and  methods  described,  if  the  crown-plates  be 
not  too  thick  and  stiff.  Of  course,  they  should  be  annealed 
before  they  are  placed  over  the  die.  In  careful  hands  the  die- 
plate  should  give  clear  cusp  definitions  after  years  of  use. 


ROOT    CROWNING. 


275 


"  For  the  reason  that  the  counter-die  plate  is  in  some  respects 
similar  to  a  stereotype  plate  for  printing,  the  struck  impressions 
on  two  strips  of  thin  plate  will  appear  as  in  Fig.  319,  wherein  their 
regular  order  is  noticeable  as  seen  from  the  cameo  surface  of  the 
struck  plates.  The  peculiar  action  of  the  hub  in  forming  first 
the  center  of  the  crown  plate,  and  spreading  from  the  center  out- 
ward, as  the  hub  is  shortened  under  the  hammer,  until  the  die 
is  overspread  by  the  plate  and  hub,  with  the  result  shown  in 
Fig.  3 18,  is  an  essential  feature  of  this  process  for  obtaining  easily 
and  quickly  the  superior  styles  of  coronal  cameos  shown.  If  a 
cusp  or  fissure  should  chance  to  crack  in  hubbing,  a  small  piece 
of  plate  may  be  struck  over  it,  or  another  crown  plate  be  struck 
over  the  first  and  the  two  soldered  together. 


Fig.  318. 


"  The  depressions  in  the  struck  plate  can  be  partly  or  wholly 
filled  with  scraps  of  plate  or  solder,  and  the  surplus  plate  cut 
away  from  the  cameo. 

"  The  fact  is  noteworthy  that,  by  means  of  the  Knapp  blow- 
pipe, the  coronal  intaglio  may  even  be  filled  with  melted  scraps 
cut  from  the  identical  plate  out  of  which  the  cameo  was  struck. 
The  better  way,  however,  is  to  fill,  say,  a  twenty-carat  cameo 
with  eighteen-carat  plate  scraps.  -The  fitting  and  soldering  of 
the  doubled  or  filled  cameos  to  suitable  collars  is  a  simple  matter, 
and  need  not  be  described. 

"  It  only  remains  to  add  the  statement  that,  by  this  counter- 
die  and  hub  process,  gold,  platinum,  silver,  or  other  metallic  cap- 


2/6 


MECHANICAL    DENTISTRY. 


crowns,  having  finely-formed  and  solid  cusps  for  proper  occlusion 
and  resistance  to  wear,  can  be  made  with  little  trouble  and  in  a 
very  short  time." 

After  securing  a  well-defined  occluding  surface  or  cameo  for 
the  case  in  hand,  it  should  be  filled  with  gold  plate  scraps  or 
solder  of  a  lower  carat,  with  a  little  borax.  This  is  all  held  over 
a  Bunsen  burner  until  the  small  pieces  of  gold  come  to  the  fusing 
point  and  settle  down  into  the  depressions  of  the  shell.     More 

Fig.  319. 


4- 


small  pieces  should  then  be  added  until  it  is  level  full.  The 
surplus  gold  should  then  be  trimmed  away,  and  a  file  passed 
several  times  over  the  surface  of  the  solder  to  bring  it  down  per- 
fectly level  and  smooth.     (See  Figs.  320  and  321.) 

Before  removing  the  band  from  its  position  in  the  mouth,  a 
small  mark  should  be  made  with  an  excavator  to  indicate  the 
center  of  the  buccal  surface,  which  will  serve  as  a  guide  for  the 
correct  placement  of  the  cusps.     By  giving  the   band  and  the 


ROOT    CROWNING. 


277 


cusps  a  smooth  surface  with  the  file,  as  has  been  directed,  it  will 
be  found  that  an  accurate  joint  between  them  can  readily  be 
secured. 

Having  carefully  noted  the  line  of  occlusion  and  marked  the 
band  to  indicate  the  point  where  the  center  of  the  buccal  surface 
of  the  cusps  or  crown-plate  should  be  placed  and  soldered,  the 
two — the  band  and  the  crown-plate — should  be  carefully  brought 
together  and  secured,  either  with  a  few  strands  of  small  binding 
wire  or  with  suitable  pliers,  as  shown  in  Fig.  322.  The  joint  should 
now  be  coated  with  borax  dissolved  in  water,  when  it  is  ready  for 
the  final  soldering.  If  solder  has  been  used  in  filling  the  cusps, 
no  additional  solder  will  be  needed  at  this  time,  as  by  simply 
holding  the  crown  over  the  flame  of  a  Bunsen  burner  as  shown 
in  Fig.  322  until  the  solder  is  seen  to  come  to  the  fusing  point. 


Fig.  322. 


then  instantly  withdrawing  it,  the  crown-plate  and  band  will  be 
united  perfectly.  If,  however,  gold  plate  has  been  used  entirely 
in  forming  the  crown-plate,  a  small  piece  of  solder  will  be  needed 
to  unite  them.  The  crown  is  then  ready  for  the  finishing  pro- 
cesses, which  consist  in  filing  or  grinding  off  the  projecting 
edges  of  the  crown-plate  flush  with  the  face  of  the  crown, 
and  smoothing  and  beveling  the  free  edge  of  the  band  or 
ferrule  ;  the  crown  should  then  be  adjusted  to  the  root  and  the 
occlusion  noted.  If,  as  is  frequently  the  case,  a  little  of  the 
gold  needs  to  be  removed  at  one  or  more  points,  in  order  to 
have  a  perfect  occlusion,  it  should  be  done  with  a  small,  flat- 
faced  corundum-stone.  The  crown  should  then  be  removed 
and  polished  at  the  lathe. 

"  Gold  Seamless  Contour  Crowns." — The  manner  of  con- 


278 


MECHANICAL    DENTISTRY. 


structing  what  is  known  upon  the  market  as  the  "  Evans  Gold 
Crowns  "  we  here  present,  through  the  courtesy  of  Dr.  George 
Evans,  who  says: — 

The  artistic  requirement  of  all-gold  crown-work  is,  that  it  shall 
reproduce  the  anatomical  contour  of  the  natural  teeth.  This  is 
usually  accomplished  by  melting  solder  on  the  collar  and  then 
trimming  it  to  the  form  of  the  crown.  A  preferable  method  is 
to  shape  the  metal  forming  the  sides  of  the  crown  by  swaging. 
This  is  easily  done  in  a  crown  formed  in  sections,  but  a  special 
process  is  required  in  the  construction  of  seamless  crowns. 

A  contour  crown  can  be  made  by  placing  a  seamless  cap  on  a 
sectional  die  or  mandrel  of  the  shape  of  the  tooth,  first  swaging 
the  grinding-surface  on  the  mandrel  and  then  stamping  down- 
ward on  the  straight  sides  of  the  crown  with  a  cap  fitted  to  the 
shank  part  of  the   mandrel.     But  such  a  process,  like    many 


Fig.  323. 


Fig.  324. 


Fig.  325. 


others,  is  too  complicated  to  be  of  any  use  to  the  dental  prac- 
titioner. The  sectional  mold  method  here  presented  is  simple, 
practical,  and  general  in  its  application. 

To  describe  and  illustrate  the  process,  we  will  take  one  of  the 
most  difficult  crowns  to  construct — a  superior  molar  (Fig.  323). 
A  natural  tooth,  or  one  made  of  plaster,  is  used  as  a  model. 
From  this  a  sectional  mold  is  made,  as  illustrated  in  Figs.  324 
and  325,  in  Babbitt's  metal,  zinc,  or  fusible  alloy.  Into  the  mold 
a  cap  of  gold  (F'ig.  326)  23  to  24  carats  fine,  30  to  32  gauge,  is 
adjusted,  fitting  tightly  the  orifice  of  the  closed  mold.  The 
mold  is  placed  in  a  vise,  the  cap  expanded  to  the  general  form 
of  the  mold  by  hammering  into  it  a  mass  of  cotton,  and  then 
swaged  more  in  detail  to  the  form,  and  with  a  wood  point  or  a 
burnisher  revolved  by  the  dental  engine  burnished  into  every 


ROOT    CROWNING. 


279 


part  of  the  mold  (Fig.  327).  To  facilitate  the  process,  the  mold 
should  be  frequently  opened  and  the  gold  annealed.  Fig.  328 
represents  the  completed  crown.  These  results  can  be  secured 
by  other  styles  of  molds. 

Another  method  is  to  form  a  fusible-metal  die  of  the  tooth  to 
be  crowned,  and,  after  having  stamped  the  grinding-surface  of 
the  crown,  to  reverse  and  swage  the  sides  close  to  the  die ;  the 
crown  is  then  relieved  of  the  core  (die)  by  heating  to  the  melting 
point  of  the  fusible  metal  and  pouring  it  out. 

For  practical  use,  a  variety  of  molds  is  required,  made  from 
natural  teeth  of  different  sizes  and  average  forms  to  serve  in 
corresponding  cases.  The  crowns  can  be  contracted  at  the  neck- 
more  than  their  size  and  contour  call  for,  so  that  the  gold  will 


Fig.  327. 


^.^^:^^^^s^ 


Fig.  329. 


act  as  a  tight-fitting  band,  which  will  expand  to  the  form  of  the 
root  as  the  crown  is  pressed  up  in  the  process  of  adjustment. 

Caps  of  metal  can  be  made  in  different  sizes  and  kept  on 
hand  for  use  in  this  and  other  styles  of  crown-work  by  means 
of  a  machine  which  in  principle  is  such  as  is  used  by  jewelers 
for  forming  cap-shaped  pieces  of  gold,  and  in  factories  for 
making  copper  cartridges.  The  gold  plate,  cut  into  circular 
pieces,  is  pressed  through  a  steel  die-plate,  with  punches  gauged 
to  the  holes  ;  at  each  punch  a  small  portion  of  the  gold  is  turned 
over,  thus  preventing  its  lapping  or  creasing.  Repeated  anneal- 
ing of  the  metal  is  very  necessary  in  this  process. 

Methods  of  Contouring  Crowns  Constructed  in  Sec- 
tions.— In  constructing  a  crown  in  sections,  the  collar  can  be 


28o 


MECHANICAL    DENTISTRY. 


first  formed  on  a  mandrel,  then  placed  in  a  mold,  and  burnished 
to  the  shape  of  the  sides.  The  process  of  its  adjustment  to  the 
neck  of  the  root  is  then  continued  in  the  usual  manner. 

Another  method  is  to  stamp  or  burnish  up  the  collar  on  a  die 
representing  the  upper  sections  of  a  tooth,  designated  as  the 
middle  and  cervical  third  (Fig.  329).  After  contouring  the 
collar,  the  cap  is  adjusted  and  soldered  on.  With  a  metallic 
stamping  plate  (see  page  273)  these  caps  are  quickly  made. 

The  Selection  and  Adjustment  of  Seamless  Contour 
Crowns. — A  superior  molar — one  of  the  most  difficult  teeth  to 
operate  on — will  serve  as  a  typical  case  to  illustrate  this  process. 
The  crown  or  root  is  first  shaped  and  if  necessary  built  down 
with  amalgam,  straight,  or  tapering  slightly  on  its  sides  toward 
the  occluding  surface. 

The  width  of  the  crown  required  from  the  anterior  to  the 
posterior  sides  of  the  occluding  surface  is  first  obtained  by 
measurement  with  a  piece  of  card-board  or  thin  copper  plate,  as 
shown  at  A,  Fig.  330.  The  measurement 
can  be  taken  direct  from  the  mouth,  or 
more  conveniently  from  a  small  plaster 
cast  made  from  a  correct  impression  of 
the  prepared  crown  or  root  and  the  two 
approximal  teeth.  This  measurement  can 
also  be  taken  by  means  of  tweezers  with 
a  set-screw  (Fig.  331).  With  this  measurement  as  a  guide,  the 
proper-sized   occluding   surface  is   readily  found   by  comparison 


Fig. 


Fig.  331. 


Tweezers  with  Set-screw  to  use  as  Calipers. 


with  the  dimensions  of  the  various  crowns  as  shown   on  the 
printed  chart  of  the  crowns  (C,  Figs.  332  and  333). 

The  size  of  the  neck  can  be  calculated  by  the  eye,  or  by  taking 
the  dimensions  with  a  piece  of  fine  wire  (Fig.  336),  pressing  the 


ROOT    CROWNING. 


281 


wire  on  the  surface  of  a  piece  of  sheet  wax,  and  then  comparing 
with  the  impression  the  necks  of  the  gold  crowns. 

In  making  a  selection,  it  should  be  borne  in  mind  that  the 
cervix  of  the  gold  crown  should  preferably  be  smaller  than 
larger,  as  it  can  alwavs  be  easily  expanded,  while  its  contraction 
is  difficult.  It  is  not  essential  that  the  curve  of  the  collar  shall 
correspond  with  that  of  the  tooth,  as  the  gold  will  readily  take 
the  proper  shape  as  the  crown  is  adjusted. 

Method  of  Adjusting  the  Crown. — i.  Anneal  the  crown 
selected,  and  slip  it  over  the  end  of  the  natural  crown  or  root 
and  gently  press  or  work  it  upward — the  gold  of  the  collar  will 


expand  to  the  form  of  the  root  in  the  operation — until  the  edge 
meets  the  margin  of  the  gum  (A,  Fig.  334). 

2.  Mark  a  line  (B)  on  the  gold  parallel  with  the  margin  of  the 
gum. 

3.  Remove  and  trim  to  this  line  (A,  Fig.  337).  If  necessary 
repeat  the  marking  and  trimming  until  the  edge  meets  the  gum 
evenly. 

4.  Bevel  the  edge  of  the  gold,  readjust  the  crown,  and  press  it 
up  until  the  edge  of  the  collar  passes  under  the  margin  of  the 
gum,  and,  if  the  occlusion  is  correct,  burnish  the  gold  to  the 
cervix. 


282 


MECHANICAL    DENTISTRY. 


To  Expand  the  Collar  and  Crown. — If  the  collar  of  the 
crown  needs  enlargement,  it  is  easily  and  most  properly  accom- 
plished with  crown  expanders  (shown  in  miniature  form  in  Fig. 
338),  the  points  of  which  should  be  introduced  at  first  just  with- 
in the  edge  of  the  neck,  and  the  gold  spread  sufficiently  to  allow 
it  to  fit  over  the  end  of  the  natural  crown  or  root,  the  process  of 


Fig.  335. 


Fig.  336. 


Fig.  337. 


expansion  being  gradually  continued  as  the  crown  is  brought 
into  position.  By  proceeding  in  this  manner  too  great  expan- 
sion is  avoided. 

If  the  entire  crown  needs  enlargement,  it  is  best  done  by  soft- 
ening a  mass  of  gutta-percha  of  aboutthe  same  size  as  the  crown 
upon  the  closed  ends  of  a  pair  of  expanding  or  clamp  forceps, 
which  are  heated  for  the  purpose.     The  forceps  points  with  the 
Fig.  338.  gutta-percha    are    then    introduced      pic.  339. 

inside  the  collar  of  the  crown,  which 
should  be  moistened  to  prevent  ad- 
hesion. The  gutta-percha  is  next 
withdrawn,  hardened  in  cold  water, 
and  cut  through  the  center  between 
the  points  of  the  forceps.  This 
makes  practically  an  expanding  sectional  man- 
drel with  which  the  crown  can  be  enlarged  ac- 
cording to  the  position  in  which  the  forceps 
were  introduced  (Fig.  339). 

To  expand  the  crown  without  enlarging  the 
neck,  trim  off  the  gutta-percha  on  the  forceps 
at  the  neck. 

The  naked  points  of  an  ordinary  clamp  forceps  can  sometimes 
be  used  to  advantage  in  expanding  a  portion  of  the  coronal 
section  of  the  crown. 


ROOT    CROWNING. 


28- 


To  Alter  a  Side. — The  contour  of  one  or  both  sides  can  be 
depressed  and  the  crown  thus  narrowed  by  introducing  the 
points  of  a  crown  expander  or  some  tool  that  will  fit  loosely  in- 
side the  crown,  then  steadying  the  crown  with  the  fingers,  as 
shown  in  Fig.  340,  and  tapping  the  sides  to  be  reduced  with  the 
flat  end  of  a  riveting  hammer.  This  is  necessary  when  the 
contour  or  tlie  side  of  a  crown  presses  on  an  adjoining  tooth,  and 
the  crown  is  thus  prevented  from  coming  in  proper  position. 

To  Alter  the  Shape  of  a  Portion  of  the  Collar  or  Side  of  a 
Crown. — Slip  the  crown  over  the  point  of  an  anvil,  the  end 
of  a  pair  of  expanders,  or  a  small  round-handled  instrument  held 
in  a  vise,  then  tap  the  part  to  be  altered  with  the  flat  end  of  a 
rivetine  hammer  to  the  form  desired. 


Fig.  340. 


Fig.  341 


To  Alter  the  Occluding  Surface. — Before  the  crown  is 
pressed  up  to  its  apparently  proper  position,  the  occlusion  should 
be  examined,  and  calculations  carefully  made  to  obviate  any  de- 
fects of  articulation,  which  can  be  readily  corrected  at  this  stage 
by  proper  manipulation  of  the  crown.  Any  necessary  change 
in  the  form  of  the  occluding  surface  can  be  made  with  the  crown 
in  position  on  the  tooth,  by  means  of  an  instrument  tapped  by 
the  mallet ;  by  removing  the  crown,  placing  it  over  the  closed 
points  of  an  expander,  and  tapping  and  burnishing  the  part ;  or 
by  holding  the  crown  between  the  thumb  and  forefinger  with  the 
edge  of  the  collar  resting  on  the  side  of  the  next  finger,  which 
when  necessary  can  be  protected  with  a  napkin,  and  then  tapping 
the  gold  with  the  point  of  a  riveting  hammer  (Fig.  341). 


284  MECHANICAL    DENTISTRY. 

The  occluding  of  the  antagonizing  teeth  on  the  crown  by  the 
patient  will  assist  and  complete  the  process  of  articulation. 

To  Contract  the  Neck. — Slightly  bend  in  the  edge  of  the 
gold  at  the  neck  with  narrow-beaked  pliers,  and,  holding  the 
crown  evenly  and  firmly  between  the  fingers,  as  shown  in  Fig. 
342,  burnish  the  sides  of  the  neck  section  inward  around  the 
entire  circumference  of  the  crown. 

To  Considerably  Contract  a  Crown. — Slit  the    gold    longi- 
tudinally at  the  palatal  or  lingual  side  its  full  length  to  the  grind- 
ing-surface,  bevel   off   the    edge   to   lap 
Pig.  342.  under,      contract    the      crown,     readjust 

^"77^^^^  to  the  tooth,  remove,  place  the  smallest 

v/         ^^^?  quantity  of  dampened  fluxed  solder  filings 

|^4>  ^^      )  in  the  seam  on  the  inside  of  the  croivn  only, 

^^^^^r^  )!^  and  solder  by  holding  in  an  alcohol  flame. 

^^;ggrg^i^^3K**^     ^    Then  proceed  with  the  further  adjustment 
-i^     ^^j  of  the  crown. 

\\     ^^-^iiig^  The  outside  line    of  the  seam   can  be 

'  ^i^^^*""^^  stoned  off  and  polished  after  the  crown  has 

been  fitted,  and  additionally  soldered  to 
strengthen  the  sides  or  grinding-surface. 

Strengthening  Seamless  Gold  Contour  Crowns. — Addi- 
tional strength  and  stiffness  can  be  given  to  seamless  gold  crowns, 
when  desired,  in  several  ways.  The  liability  of  melting  the  gold 
which  forms  the  sides  of  the  crown  in  the  operation  has,  with 
some,  been  the  principal  objection  to  their  use.  This,  however, 
can  be  avoided. 

When  the  crown  has  been  properly  adjusted,  dampen  the  inner 
surface  with  a  piece  of  wet  cotton  on  the  point  of  an  instrument ; 
place  in  the  interior  a  quantity  of  fluxed  solder  filings  (solder 
filings  mixed  with  Parr's  flux  or  pulverized  vitrified  borax) ; 
place  the  finger  over  the  open  end  of  the  crown,  invert,  and 
shake  well.  A  portion  of  the  solder  filings  will  adhere  evenly 
all  over  the  wet  surface.  The  surplus  is  allowed  to  drop  out  by 
removing  the  finger.  Then  gradually  and  uniformly  heat  the 
crown  by  holding  it  with  tweezers  in  an  alcoliol  flame  (not  gas) 
until  the  solder  fuses,  when  it  will  flow  evenly  over  the  surface 
of  the  gold  without  materially  altering  the  general  form.     The 


ROOT    CROWNING.  285 

crown  should  be  held  in  such  a  position  that  a  full  view  of  the 
interior  is  presented  and  the  melting  of  the  solder  rendered 
visible,  which  will  occur  at  a  red  heat. 

An  extra  quantity  of  the  solder  filings  can  be  placed  in  the 
interior  of  the  cusps  with  a  spoon-shaped  excavator  to  addition- 
ally fill  or  strengthen  them  if  found  necessary. 

When  a  Biinscn  gas  flavie  is  used  instead  of  an  alcohol  flame, 
the  grinding-surface  and  sides  of  the  crown  should  be  first  coated 
with  whiting.  This  is  easily  done  by  dipping  the  crown  into  a 
cream-like  mixture  of  whiting  just  before  inserting  it  in  the 
flame.  The  moisture  in  the  whiting  should  be  first  slowly 
evaporated  by  heating  up  gradually.  Great  care  must  be  exer- 
cised in  the  use  of  a  gas  flame  to  avoid  melting  the  crown. 
The  crown  should  be  watched,  and  instantly  removed  as  soon  as 
the  solder  fuses  and  flows. 

If  too  much  solder  has  been  applied  at  any  point,  it  can  be 
trimmed  and  smoothed  with  corundum  melted  on  to  an  old 
engine  bur-point.  Always  boil  the  crown  in  acid  to  remove  the 
flux.  The  removal  of  flux  from  the  inner  surface  of  the  crown 
is  absolutely  necessary  if  you  intend  to  use  it  in  bridge-work,  as 
solder  will  have  to  be  melted  on  the  outside. 

To  Repair  a  Gold  Crown. — When  a  hole  is  cut  or  melted  in 
any  kind  of  a  gold  crown,  place  a  piece  of  soft  wax  in  the  aper- 
ture on  the  outside  of  the  crown,  adapt  on  the  inside  close 
against  the  gold  a  piece  of  platinum  foil,  somewhat  larger  than 
the  aperture,  so  that  it  will  adhere  to  the  wax.  Fill  the  interior 
of  the  crown  with  investing  material,  and  flow  a  little  solder  over 
the  surface  of  the  platinum  and  gold  on  the  outside  of  the 
crown. 

Gold  seamless  crowns  can  also  be  strength-  Fig.  343. 

ened  or  filled  with  solder,  or  even  18-  or  20-     ^^grgps 
carat  gold  plate,  by  investing  the  outside  sur- 
face in  plaster  and  marble-dust  (Fig.  343),  and 
then  with  a  small  flame  of  the  carbo-oxyhy- 
drogen  blowpipe,  not  over  one-half  an  inch  in         ^ 
length,   introduced  inside   of  the   crown,   melt         ^ 
and  flow  the  solder  or  gold  plate  over  any  por-        j 
tion  or  even  all  of  the    surface    of  the   srold. 


286  MECHANICAL    DENTISTRY. 

The  crown,  if  formed  of  gold  with  a  thin  lining  of  platinum,  can 

be  soldered  by  either  method  with  little  danger  of  being  melted. 

Supporting  the   Crown. — In    crowning     teeth    with    living 

pulps  there  is  sufficient  of  the  natural  crown  present  to  afford  a 

secure  foundation  and  attachment  for  the  artificial  crown,  as  is 

also  the  case  with  many  teeth  that  are  pulpless ;  but  in  badly 

broken-down  crowns,  or  where  only  the  root  is  present,  a  metallic 

pin  or  post  should    be  inserted    in  the  root,  and  the  part  built 

down  with  amalgam  to  a  form  which  will  afford  se- 
FiG.  344.  ° 

cure  support  and  attachment  to  the   artificial  crown 
and  facilitate  its  adjustment. 

In  many  cases  the  required  support  for  the  crown 
can  be  secured  by  means  of  a  screw  (Fig.  344).  A 
How  screw  or  a  post  of  silver  wire  is  inserted  in  the 
root-canal  A  (see  page  208).  Amalgam  is  then  packed 
in  the  lower  section  of  the  artificial  crown,  C,  to  the 
line  B,  and  into  the  amalgam  the  screw  is  pressed. 
Amalgam  which  has  been  put  in  a  piece  of  chamois 
and  the  mercury  pressed  out  with  a  pair  of  pliers  until  it  is  in 
the  condition  termed  "dry  "will  adhere  to  the  gold  without 
affecting  it.  The  amalgam  is  first  placed  in  the  crown  slightly 
in  excess  of  the  amount  required,  and  the  crown  adjusted,  re- 
moved, and  the  surplus  scraped  out.  This  process  is  continued 
until  the  screw  or  the  crown  section  of  the  natural  tooth  forms 
an  indentation  in  the  amalgam,  which  it  will  fit  when  the  crown 
is  cemented  on.  The  vent  for  the  escape  of  air  and  surplus 
cement — which  should  always  be  put  in  perfect-fitting  crowns 
and  afterward  filled  with  gold  or  amalgam — should  be  in  the  line 
of  the  indentation  in  the  amalgam,  with  which  it  must  connect 
(D). 

These  crowns  can  be  inserted  in  an  easy  and  inexpensive  man- 
ner by  filling  in  the  lower  section  of  the  crown  with  amalgam 
instead  of  gold,  and  allowing  the  head  of  the  screw  or  the 
natural  crown  to  indent  the  amalgam  as  above  described,  and 
then  cementing  on  the  crown  with  oxyphosphate  in  the  usual 
manner. 

In  a  case  so  inserted,  with  no  antagonizing  teeth,  the  result  is 
the  same  as  though  the  inside  of  the  occluding  surface  of  the 


BRIDGE-DENTURES.  28/ 

crown  was  filled  with  gold ;  but  if  antagonizing  teeth  are  pres- 
ent, the  gold  of  the  crown  is  apt  to  wear  through  in  places  and 
expose  the  amalgam. 

To  Securely  Attach  a  Crown. — If  the  tooth  is  short,  and 
the  occlusion  of  a  character  requiring  the  reduction  of  the 
collar  to  such  a  degree  as  to  suggest  insecurity  when  the  crown 
is  cemented,  a  barbed  or  headed  pin,  which  will  anchor  in  the 
natural  crown  or  root,  should  be  soldered  in  the  center  of  the 
gold  crown.  This  is  done  by  passing  the  pin  through  a  hole 
drilled  in  the  occluding  surface  of  the  crown,  which  is  then 
adjusted  in  the  mouth,  removed,  invested,  and  the  pin  soldered 
from  the  outside.  If  the  pin  is  tapered  and  fitted  tightly  to  the 
hole,  the  soldering  can  be  accomplished  without  investing,  by 
holding  the  crown  and  pin  with  solder  in  position  in  an  alcohol 
flame. 

To  Alter  a  Gold  Crown  to  the  Exact  Form  of  any  Cor- 
responding Natural  One. — In  a  case  having  nearly  all  the 
natural  teeth  present,  in  which  the  occluding  surface  and  sides 
differ  in  shape  from  the  form  of  the  gold  crown,  to  such  an 
extent  as  to  interfere  with  its  adjustment,  a  die  of  the  natural 
crown  should  be  made  of  fusible  metal  (Melotte's  Fusible  Alloy), 
and  with  it  the  interior  of  the  gold  crown  should  be  altered  in 
shape  sufficiently  to  receive  the  natural  crown,  by  resting  the 
occluding  surface  of  the  gold  crown  on  a  folded  napkin  and 
gently  tapping  the  die  into  it. 

The  advantages  of  seamless  contour  crowns  are,  that  they 
represent  perfectly  the  tooth  in  its  anatomical  contour,  present 
a  uniform  surface  of  pure  gold,  which  preserves  its  color  with- 
out tarnishing,  and  are  quickly  and  easily  adjusted.  Their 
defects  are  inability  to  meet  the  requirements  of  abnormally- 
shaped  roots  and  anomalous  articulations. 


Bridge- Dentures. 

To  the  skilled  dentist,  well  versed  in  crown-work,  bridge-work 
does  not  present  any  great  difficulty,  inasmuch  as  crowns  are 
the  beginning  and  the  end ;  it  is  practically  continuous  crown- 
work,  though   many  of  the   crowns — those  filling   or  bridging 


288  MECHANICAL    DENTISTRY. 

the  space  where  the  roots  have  been  removed — have  neither 
collars  nor  posts.  In  constructing  these  teeth,  the  matter  of 
cleanliness  should  especially  be  considered ;  where  it  is  admis- 
sible to  allow  them  to  come  in  contact  with  the  gum-tissue  (as 
in  the  anterior  part  of  the  mouth),  only  the  cervical  porcelain 
tips  should  touch.  The  metallic  backing  and  solder  should 
recede,  leaving  self-cleansing  spaces. 

Some  diversity  of  opinion  exists,  however,  as  to  the  advisa- 
bility of  permanently  fixing  such  appliances  in  the  mouth. 
Prominent  among  the  objections  urged  is,  that,  in  the  event  of 
accident  to  the  porcelain  facing  of  the  crown,  there  is  no  suffici- 
ent remedy  without  detaching  the  entire  piece,  of  which  the 
teeth  are  a  part.  It  is  further  objected  that  a  stationary  fixture 
of  this  kind  in  the  mouth  must  become  not  only  offensive  from 
the  accumulation  and  retention  of  oral  debris  incapable  of 
adequate  dislodgment,  but  a  source  of  injury  to  the  remaining 
natural  teeth,  which  necessarily  follows  the  prolonged  retention 
of  alimentary  substances  exposed  to  conditions  so  favorable  to 
fermentation  and  putrefactive  decomposition. 

On  the  other  hand,  the  writer  entirely  agrees  with  many  com- 
petent, intelligent,  and  conscientious  operators,  who,  from 
observation  and  experience  are  qualified  to  form  a  just  estimate 
of  the  merits  or  demerits  of  bridge-dentures,  and  who  bear  testi- 
mony in  unqualified  commendation  of  its  superior  excellence 
when  skilfully  performed  under  conditions  that  justify  the  opera- 
tion, and  claim  for  it  as  complete  exemption  from  the  alleged 
objections  as  is  obtained  in  the  use  of  any  other  mode  of  re- 
placement in  similar  cases. 

In  fact,  herein,  we  think,  lies  the  secret  of  either  success  or 
failure  in  connection  with  bridge-dentures,  for  it  is  in  the  con- 
struction of  this  class  of  dentures,  more  than  any  other,  that 
unusual  mechanical  skill  is  required,  and  professional  judgment 
needed  for  determining  where  they  are  admissible. 

Limitations. — For  the  support  of  bridge-dentures  strong, 
healthy  roots  are  required,  and  the  width  of  the  space  to  be 
spanned  must  be  governed  by  the  size  and  strength  of  these 
points  of  anchorage.  Whether  a  full  upper  or  lower  denture 
can  be  supported  by  four  points  of  attachment  depends  upon  the 


BRIDGE-DENTURES.  289 

relative  smallness  of  the  jaw,  the  size  and  strength  of  the  roots 
and  teeth,  and  the  occlusion,  the  operator  always  being  gov- 
erned by  the  exact  condition  of  individual  cases. 

Before  entering  upon  a  more  general  consideration  of  the 
subject,  it  may  be  helpful  to  give  a  few  reflections  or  sugges- 
tions in  the  way  of  typical  cases,  as  follows  : — 

One  strong  central  root  will  support  two  teeth,  that  is,  the 
crown  and  either  the  adjoining  central  or  lateral.  Two  central 
roots  will  support  the  four  incisors.  Two  strong  cuspid  roots 
alone,  or  with  the  aid  of  a  central  root,  will  support  the  six 
anterior  teeth.  A  cuspid  root  and  a  strong,  healthy  second  or 
third  molar  on  the  same  side  will  support  the  intervening  teeth. 
One  molar  or  bicuspid  on  one  side,  and  a  bicuspid  or  molar  on 
the  other,  with  one  or  two  central  roots,  will  support  a  bridge 
between  them.  One  right  and  one  left  molar,  with  the  assistance 
of  the  two  cuspid  roots,  when  the  conditions  are  favorable,  as 
spoken  of  above,  will  support  a  bridge  comprising  the  entire 
arch. 

It  should  be  rememberedthat  the  preparation  of  the  teeth  and 
roots  for  the  support  of  a  bridge  is  the  same  as  in  ordinary 
crown-work,  except  that  the  trimming  of  the  sides  and  the  drill- 
ing of  the  root-canals  should  be,  as  far  as  possible,  in  parallel 
lines,  so  that  in  the  adjustment  of  the  finished  piece  the  crowns 
will  move  readily  to  their  place. 

STATIONARY    BRIDGE-DENTURES. 

Among  the  simpler  forms  of  substitution  which  may  be  pro- 
perly classed  under  the  head  of  "  bridge-work,"  is  the  one  in 
which  a  single  artificial  crown  derives  support  from  attachments 
made  to  one  or  more  of  the  adjoining  natural  teeth,  originally  by 
a  process  of  cavity-filling.  The  original  conception  and  practical 
application  of  such  a  method  of  supplying  an  edentulous  space 
is  attributed  to  Dr.  B.  J.  Bing,  of  Paris,  France,  whose  method  of 
operating  has  since  been  greatly  modified. 

Dr.  Webb's  Method. — One  of  the  earlier  experimenters  in 
this  mode  of  replacement  was  the  late  Dr.  Marshall  H.  Webb, 
who  thus  describes  his  method  of  operating  in  these  cases  : — 

"  The  insertion  of  a  crown  without  plate  or  clasps,  where  no 
19 


290  MECHANICAL    DENTISTRY. 

root  remains,  is  a  difficult  operation,  but  when  well  performed, 
and  the  crown  attached  to  teeth  that  are  firm  in  their  sockets,  it 
is  both  satisfactory  and  permanent. 

"  The  first  such  operation  performed  by  the  writer  was  com- 
pleted February  12,  1873,  and  the  crown  now  remains  as  firm 
as  when  inserted.  The  operation  was  performed  in  the  following 
manner  :  After  suitably  forming  the  cavities  in  the  proximate 
wall  of  each  tooth  next  the  space  left  by  the  loss  of  the  one  that 
had  been  extracted  (unnecessarily)  some  years  before,  an  impres- 
sion of  the  parts  was  taken,  and  a  plain  porcelain  crown  was 
selected,  fitted  to  place,  and  backed  with  gold  plate  (18  k.).  A 
portion  of  the  backing  extended  about  one  and  a  half  lines  from 
each  side  of  the  crown  for  insertion  in  the  cavities  prepared  in 
the  adjoining  teeth,  and  to  these  parts  a  gold  wire  was  soldered 
to  fit  into  the  pulp-chamber  of  the  central  and  lateral  incisors. 
A  small  gold  plate  was  then  formed  to  fit  upon  the  gum,  cover- 
ing as  much  space  as  was  taken  up  by  the  neck  of  the  natural 
tooth.  The  backing  was  riveted  to  the  pins  in  the  porcelain, 
and  this  placed  in  position,  and  while  the  whole  rested  on 
the  small  plate  upon  the  gum,  the  backing  and  plate  were  so 
secured  by  wax  that  they  could  be  removed  intact,  and,  after 
being  placed  in  a  matrix,  soldered.  Each  extended  side  of  the 
backing  and  the  surface  of  the  wire  was  barbed  with  an  en- 
graver's bossing  tool,  so  that  the  gold  foil  would  the  better  secure 
the  crown  when  filled  into  every  part. 

"  The  porcelain,  with  the  gold  attachments,  being  ready  for 
insertion,  a  piece  of  light,  medium  rubber-dam  was  put  in  place 
on  two  teeth  each  side  of  the  space  to  be  filled,  and  over  the  gum 
upon  which  the  crown  was  to  rest.  (The  rubber  takes  up  but 
little  space,  and  this  is  more  than  compensated  for,  when  the 
ligature — waxed  floss-silk — is  pressed  to  or  near  the  neck  of 
each  adjoining  tooth.)  Oxychlorid  of  zinc  was  then  placed  in 
the  pulp-chamber  of  the  central  incisors  and  the  crown  at  once 
pressed  to  place.  When  the  cement  had  hardened  sufificiently  to 
safely  admit  of  further  progress  in  the  work,  a  portion  of  it  was 
cut  away  from  around  the  wire  so  as  to  make  proper  anchorage 
for  the  gold.  Small  pieces  of  light  cohesive  gold  foil  were  then 
impacted  around  part  of  the  wire  and  that  portion  of  the  plate 


BRIDGE-DENTURES. 


291 


extending  into  the  cavities,  and  the  crown  was  thus  secured. 
The  porcelain  and  gold  attachments  as  prepared  for  insertion, 
and  the  crown  in  position,  are  illustrated  in  Fig.  345. 
•  "  The  cavity  in  the  central  incisor  was  extended  to  the  cutting 
edge  of  the  tooth,  that  access  might  be  had  to  the  wire  and  both 
sides  of  the  plate ;  foil  could  not  otherwise  have  been  put  in 
place,  unless  a  portion  of  the  labial  margin  of  enamel  were  cut 
away,  and  this  would  have  been  objectionable  because  of  the 
exposure  of  gold.  A  small  part  of  the  labial  instead  of  the  cut- 
tine  edge  of  the  enamel  of  the  lateral  was  removed,  for  the 
reason  that  there  is  not  such  a  body  of  tissue  as  to  safely  allow 
it  to  be  cut  away  to  the  same  extent  as  in  a  central  incisor.     The 

Fig.  345. 


margin  of  enamel  was  so  formed,  and  the  foil  so  inserted  and 
finished,  however,  that,  though  the  gold  can  be  seen,  it  is  not 
conspicuous. 

"While  the  operation  just  described  has  thus  far  proved  suc- 
cessful, yet  there  is  a  possibility  of  the  porcelain  being  broken 
from  the  platinum  pins  which  hold  it  to  the  gold  plate.  To  avoid 
such  an  accident  a  groove  should  be  cut  on  each  side,  and  along 
the  cutting  edge  of  the  porcelain  (Fig.  346,  d),  that  gold  foil  may 
be  impacted  into  it,  after  a  heavy  backing  of  gold  plate  and  the 
wire  have  been  fixed  in  place  and  soldered.  When  the  groove 
has  been  cut  in  the  porcelain  with  a  fine-edged  corundum  disk, 
one  with  an  edge  of  the  diameter  of  the  gold  wire  selected  for 


292 


MECHANICAL    DENTISTRY. 


the  case  should  be  used  to  make  a  groove  across  the  porcelain 
between  the  pins  (Fig.  346,  a),  into  which  the  wire  to  connect 
the  artificial  crown  with  the  natural  teeth  is  to  be  placed  (Fig. 
346,  d),  either  beneath  the  plate  or  so  that  the  edges  of  the  latter 
may  be  joined  to  it,  as  the  necessities  of  the  case  may  require. 

"  A  starting-point  should  be  made  either  between  the  gold 
backing  and  porcelain,  or  between  this  and  the  wire,  and  the 
latter  firmly  fixed  in  a  hand  vise  while  the  gold  foil  is  being  im- 
pacted with  the  electro-magnetic  mallet.  When  the  gold  is 
properly  and  solidly  placed  in  the  groove  and  over  the  backing 
and  wire,  it  not  only  aids  in  securing  the  porcelain,  but  the 
contour  of  the  crown  can  be  nicely  filled  out,  and  the  operation 
made  durable  and  beautiful  (Fig.  347). 

"  The  surface  of  the  gold  placed  along  the  base  of  the  crown 


Fig.  346. 


Fig.  347. 


to  the  edge  of  the  porcelain,  and  which  is  to  rest  against  the 
gum,  together  with  the  palatal  portion,  ought  to  be  properly 
formed  and  finished  before  the  crown  is  put  in  place,  and  this 
should  be  done  in  the  manner  before  described.  There  should 
be  a  little  space  between  the  wire  and  cervical  wall  in  each  tooth 
to  which  the  crown  is  to  be  attached,  and  narrow  pieces  of  light 
gold  foil  carefully  placed  in  this  part,  between  the  wire  and 
enamel,  with  small  curved  instruments  and  the  aid  of  the 
mallet ;  the  surface  of  the  gold  at  this  part  at  least  should  be 
smoothly  finished  with  very  narrow  {^  in.)  strips  of  fine  emery- 
cloth  before  the  rubber-dam  is  removed. 

"  In  cases  where  the  pulp  is  living  in  one  or  both  of  the  teeth 
to  which  an  artificial  crown  is  to  be  attached,  the  heavy  gold 
plate  or  the  wire  must  be  so  arranged  as  to  fit  as  accurately  and 


BRIDGE-DENTURES.  293 

to  be  made  as  secure  as  possible  in  the  cavities  prepared  for 
them.  In  some  cases,  where  the  form  of  the  cavity  admits  of 
it,  it  is  better  to  adjust  and  solder  a  small  gold  plate  to  the  end  of 
and  at  right  angles  with  the  wire  attached  to  the  crown.  This 
plate  should  be  so  formed  and  beveled  that  gold  foil  can  be 
solidly  placed  over  the  surface  of  it  next  to  the  artificial  crown, 
and  into  the  groove  made  around  the  cavity  in  the  dentine  along 
the  boundary  line  between  this  tissue  and  the  enamel.  When 
all  is  in  readiness  for  the  operation,  oxychlorid  of  zinc  should 
be  placed  in  each  cavity  and  the  crown  immediately  put  in  place, 
and  very  carefully  held  there  till  the  cement  has  so  crystallized 
as  to  secure  the  ends  of  the  wire  and  plate  ;  about  an  hour  is 
necessary  to  perfect  such  crystallization  as  to  safely  admit  of  the 
preparation  for  and  the  packing  of  the  gold  foil.  The  oxy- 
chlorid of  zinc  should  be  left  between  the  little  plate  or  end  of  the 
wire  and  bottom  of  the  cavity,  and  all  parts  where  gold  cannot 
be  well  placed;  this  preparation  also  protects  the  dentinal  fibers 
from  thermal  changes. 

"  One  of  the  most  satisfactory  operations  the  writer  ever  per- 
formed was  the  insertion  of  a  crown  where  a  cuspid  root  had 
been  extracted  (unnecessarily),  and  the  lady  subjected  to  the 
wearing  of  a  gold  plate  for  some  time.  This  crown  was  pre- 
pared and  the  contour  filled  out  with  foil  as  described  (and  as 
illustrated  in  P'ig.  347),  but  gold  wire,  No.  13,  was  attached 
to  and  built  in  with  the  porcelain,  placed  into  the  pulp-chamber 
of  the  adjoining  lateral  incisor  (which  had  been  filled),  and  this 
same  wire  extended  from  the  anterior  to  near  the  posterior 
proximate  surface  of  the  first  bicuspid  tooth,  the  pulp  of  which  re- 
mained in  normal  condition.  The  crown  was  placed  in  position 
with  oxychlorid  of  zinc,  and  cohesive  gold  foil  was  then  im- 
pacted with  the  electro-magnetic  mallet  around  a  portion  of 
the  wire  in  the  root  and  into  the  cavity  in  the  crown  of  the 
incisor,  also  into  the  cavity  in  each  proximate  wall  of  the 
bicuspid  tooth,  as  well  as  around  and  over  the  wire,  joining  the 
two  fillings  through  the  enlarged  fissure. 

"  The  most  extensive  operation  of  attaching  a  crown  to  adjoin- 
ing teeth  was  performed  by  the  writer  before  the  Pennsylvania 
State  Dental  Society,  at  Delaware  Water  Gap,  in  July,  1879.    In 


294 


MECHANICAL    DENTISTRY, 


this  case  disintegration  had  taken  place  in  many  of  the  teeth, 
and  cavities  of  decay  had  been  prepared  and  filled  from  time  to 
time.  The  teeth  were  abraded  and  the  dentine  was  exposed  along 
the  entire  cutting  edge  of  each  tooth  that  occluded  with  another. 
The  right  upper  lateral  incisor  had  been  lost  twelve  years  before. 
The  crown  of  the  left  cuspid  tooth  was  missing,  and  but  a  small 
portion  of  the  enamel  and  dentine  of  the  first  bicuspid  upon 
either  side  remained.  These  last  were,  of  course,  pulpless,  as 
also  were  the  right  cuspid  and  central  and  left  lateral  incisor 
teeth,  and  the  pulp-chamber  of  each  of  these  had  been  filled.  All 
the  operations  made  necessary  by  the  abrasion  and  fracture  of 


Fig.  348. 


enamel  from  time  to  time,  and  because  of  inrperfection  in  the 
fillings  before  introduced,  were  performed  previous  to  the  inser- 
tion of  the  crown  in  the  space  left  by  the  loss  of  the  lateral 
incisor,  and,  as  this  crown  and  each  cavity  and  pulp-chamber 
was  prepared  for  the  gold,  all  appeared  as  here  illustrated  (Fig. 

348).* 

"  Gold  wire  (No.  13),  with  a  sharp  thread  cut  upon  it,  was 
screwed  into  the  dentine,  and,  at  the  same  time,  all  the  interstices 
between   the  tissue  and  the  gold  were   filled  with  oxychlorid  of 

*  The  cut  (Fig.  348)  illustrates  the   case  well,  though  there  are  parts  and  grooves 
in  which  to  anchor  the  gold,  that  are  not  distinctly  shown. — M.  H.  W. 


BRIDGE-DENTURES.  295 

zinc.  When  crystallization  had  taken  place,  some  of  the  cement 
and  dentine  was  removed  from  around  the  wire  with  a  small  bur, 
and  a  groove  was  cut  in  the  dentine  near  the  margin  of  the 
root  so  as  to  secure  proper  and  sufificient  anchorage  for  gold  ; 
cohesive  foil  (principally  No.  30)  was  impacted  into  these  parts, 
and  the  entire  contour  of  the  crown  was  restored  with  the  electro- 
magnetic mallet.  This  crown  was  not  faced  with  porcelain,  be- 
cause the  teeth  of  the  gentleman  for  whom  these  operations  were 
performed  are  but  slightly  exposed  to  view  ;  and  then,  too,  the 
gold  had  to  be  placed  over  the  enamel  to  support  and  protect 
it  along  the  cutting  edges  of  all  the  incisor,  the  cuspid  and  bi- 
cuspid teeth.  A  gold  screw  was  placed  in  the  pulp-chamber  and 
extended  into  the  crown  of  each  bicuspid  tooth  (Fig.  348).  The 
apical  foramen  of  each  pulpless  tooth  was  closed,  and  the  whole 
of  each  pulp  chamber  into  which  a  wire  was  not  placed  was 
filled  with  gold.  With  a  properly  adjusted  electro-magnetic  mallet, 
carefully  guided,  and  operated  with  a  full  current  of  electricity 
from  a  freshly-charged  four-cell  Bunsen  battery,  the  contour  of 
each  crown  was  restored  with  gold,  made  solid  and  perfect 
throughout ;  the  foil  was  placed  in  the  same  manner  over  the 
finely  prepared  margins  of  enamel,  which  were  not  marred  in 
the  least  (Fig.  349). 

"  The  lower  incisor  teeth  had  so  changed  after  the  loss  of  the 
upper  lateral  that  they  almost  closed  upon  the  gum.  This  was 
partly  owing  to  the  abrasion  of  the  remaining  teeth,  and  in  part 
due  to  the  lower  incisors  gradually  rising  in  the  alveolar  process. 
Because  of  such  occlusions  of  the  teeth  a  porcelain  crown  (plain 
'  plate  tooth  ')  with  '  cross-pins  '  was  used,  and  fitted  and  soldered 
to  the  gold  wire,  there  being  no  space  for  a  backing  of  plate. 
When  the  wire  was  prepared,  the^porcelain  grooved  and  fitted  to 
it,  and  ready  for  the  placing  on  of  the  gold  foil,  the  whole 
appeared  as  illustrated  (Fig.  348),  the  wire  extending  into  each 
root  about  four  lines.  The  cutting  of  the  porcelain  was  removed 
to  the  same  extent  as  that  of  the  abraded  and  prepared  incisors, 
so  as  to  present  the  same  appearance  and  have  the  gold  support 
and  protect  the  remaining  part.  The  wire  of  the  crown  was 
held  in  a  hand-vise,  while  cohesive  gold  foil  was  placed  solidly  in 
the  grooves,  around  the  wire,  over  the  cutting  edge  of  the  porce- 


296 


MECHANICAL    DENTISTRY. 


lain,  and  the  entire  contour  restored  with  the  electro-magnetic 
mallet.  During  the  final  fitting  of  the  crown,  it  was  made  to  so 
rest  against  the  gum,  that  the  blood  was  pressed  from  the 
capillaries  of  the  part.  When  ready  for  insertion,  a  medium 
rubber-dam  was  applied  to  two  teeth  each  side  of  and  across  the 
space  which -was  to  receive  the  crown;  small  barbs  were  made 
all  around  the  vvire  with  a  sharp  knife,  and  oxychlorid  of  zinc 
was  then  placed  in  the  pulp-chamber  of  the  central  incisor  and 
cuspid,  and  the- crown  at  once  pressed  to  place.  After  it  had 
been  in  position  an  hour,  to  allow  of  complete  crystallization  of 
the  cement,  portions  of  this  and  of  the  dentine  were  removed 
w^ith  a  small  bur  so  as  to  better  secure  the  crown  and  obtain 
anchorage  for  the  gold  foil  then  to  be  put  in  place  around  the 
wire,  into  each   cavity,  and  over  the  prepared  margins  of  the 

-■•  FfG.  349. 


enamel.  Principally  No.  30  gold  (one-quarter  ounce  cohesive 
foil)  was  used  in  this  case,  and  all  was  impacted  with  the  electro- 
magnetic mallet,  except  a  few  pieces  of  light  foil  placed  in  the 
space  between  the  wire  and  cervical  wall,  and  even  these 
pieces  were  gone  over  with  this  very  valuable  instrument  after 
they  were  in  place.  With  this'and  all  the  operations  completed, 
the  case  appears  as  here  illustrated  (Fig.  349). 

"  All  those  who  have  the  ability  and  who  will  work  earnestly 
and  conscientiously  to  properly  perform  the  various  operations 
described,  and  do  their  very  best  in  every  case,  can  so  manage  their 
practice  as  not  to  make  it  necessary  for  any  of  the  patients  they 
have  charge  of  to  wear  artificial  teeth  mounted  upon  plates." 

Dr.  Webb's  method  of  operating  in  these  cases  was,  to  some 
extent,  subsequently  modified  as  follows  : — 


BRIDGE-DENTURES. 


297 


"  The  method,  modified  and  followed  by  the  writer,  since 
performing  his  first  operation,  is  quite  different  from  the  mode 
adopted  in  inserting  the  first  crown,  which  was  prepared 
somewhat  according  to  Dr.  Bing's  plan,  and,  though  the  work 
is  more  difficult,  yet  the  improved  crown  is  stronger  and 
more  complete,  cleanly,  and  beautiful  than  when  "gold  plate  is 
simply  riveted  and  soldered  to  the  porcelain. ,  It  was  to  avoid 
such  an  accident  as  the  breaking  of  the  porcelain  from  the  pins 


a,b,  d,f,  g,2MA  h.  Pulpless  teeth,  g.  Whole  crown  restored  with  gold,  a,/,  and 
h.  Almost  entire  gold  crowns.  The  teeth,  b  and  d,  support  the  gold  crown 
faced  with  porcelain,  c,  and  fully  one-fourth  of  the  crown  of  each  of  these  is 
restored  with  gold,  as  is  also  that  of  e,  the  pulp  of  which  is  living. 


that  the  writer  tiiodified  the  method  of  preparing  and  inserting 
crowns.  Among  the  changes  made  were  those  of  making  a 
groove  (though  not  cutting  it  too  deeply)  in  each  side  and 
along  the  cutting  edge  of  the  porcelain,  and  placing  gold  foil 
solidly  in  the  groove  and  slightly  over  the  cutting  edge, 
to  make  the  porcelain  more  secure  than  when  the  platinum  pins 
alone  hold  it,  and  to  protect  the  edge  from  the  occlusion  of  the 
lower  teeth  ;  also,  to  build  the  crown  into  the  approximal  surfaces 
only.     After   the  wire  has  been  fitted  to  the  adjoining  tooth  or 


298  MECHANICAL    DENTISTRY. 

teeth,  or  properly  placed  in  a  root,  and  a  heavy  but  rather  nar^ 
row  backing  of  gold  plate  has  been  riveted  to  the  porcelain,  and 
the  parts  are  fixed  together  and  soldered,  the  greater  part  of  the 
preparation  of  a  crown  which  remains  to  be  made,  and  the  whole 
of  the  building  of  gold  foil  about  it,  is  done  out  of  the  mouth 
at  whatever  time  may  best  suit  the  operator;  but  the  work 
requires  care,  and  must  be  skilfully  and  well  done.  A  starting- 
point  should  be  made  either  between  the  gold  backing  and  porce- 
lain or  between  this  and  the  wire,  and  the  latter  must  be  firmly 
fixed  in  a  hand-vise  while  the  gold  foil  is  being  put  in  place  and 
made  compact  with  the  electro-magnetic  mallet.  All  crowns 
should  be  prepared  and  finished  in  the  manner  described,  with 
such  change  or  additional  work  as  is  necessary  to  place  them  on 
roots,  or  to  attach  them  to  single  or  to  the  two  adjoining  teeth 
where  roots  are  missing. 

"  Methods  have  been  devised  or  adopted  with  the  object  of 
lessening  the  time  necessary  to  perform  such  operations,  and 
making  them  easy  and  cheap,  by  the  use  of  amalgam  or  some 
other  plastic  material ;  but  sufficient  time  must  be  taken, 
excellent  judgment  and  ability  are  required,  and  the  use  of  gold 
is  necessary  foi;  the  doing  of  really  fine,  beautiful,  and  permanent 
work. 

"  When  a  crown  is  to  be  attached  to  one  tooth  alone,  the 
operation  is  not  likely  to  be  successful  (excepting  where  a  bicuspid 
crown  is  built  into  a  molar  tooth),  unless  the  tooth  which  is  to 
support  the  crown  be  apulpless  one,  and  then  such  an  operation 
can  be  made  both  durable  and  beautiful.  To  secure  sufficient  an- 
chorage for  the  insertion  of  a  crown  in  such  a  manner,  therefore, 
it  may  sometimes  be  necessary  to  destroy  a  pulp  ;  but.this  ought 
to  be  the  last  resort,  and  should  be  done  only  when  calcification 
of  the  enamel  and  dentine  is  complete  or  apparently  so.  The 
end,  if  well  attained,  justifies  the  destruction  of  a  pulp  for  the 
insertion  of  a  crown,  mainly  because  of  the  beneficial  results 
which  follow.  These  are  the  longer  preservation  of  the  remain- 
ing teeth,  the  gums,  and  the  alveolar  process  in  normal  condition, 
or  the  prevention  of  the  absorption  of  the  hard  as  well  as  the 
soft  tissues  under,  and  because  of  the  pressure  of,  plates — this 
loosening  and  loss  of  teeth   sometimes  occurring  years  before 


BRIDGE-DENTURES.  299 

there  is  likely  to  be  such  solution  of  the  lime-salts  of  the  maxil- 
lary border  and  recession  of  the  gum. 

"Where  a  crown  is  to  be  built  on  to  one  tooth  only,  a  gold 
wire  no  lighter  than  No.  12  should  be  used.  It  should  be  fitted 
as  far  up  the  root  as  it  is  safe  to  enlarge  the  pulp-chamber  for 
it ;  but  the  drilling  may  be  properly  done  only  after  every  part 
of  the  pulp  has  been  removed  and  the  apical  foramen  has  been 
carefully  closed  with  small,  narrow  pieces  of  light  gold  foil, 
which  must  not  be  put  in  place  so  long  as  there  is  any  irritation 
about  the  end  of  the  root. 

"In  the  case  here   illustrated  (Fig.  351),  the  wire  is  fitted  in 
the  root  and  bent  to  receive  the  crown,  and  the  cavity  is  nearly 
prepared    for    the    filling    in  of  gold. 
The  cuspid  (as  well  as  the  other  teeth  •  ^°' 

remaining  in  the  mouth)  became  so 
abraded  as  to  expose  the  dentine,  so 
that  the  margins  of  enamel  had  to  be 
prepared  for  the  placing  of  gold  over 
them,  and  when  the  crown  was  built 
in  place,  they  were  carefully  covered 
with  and  are  thus  protected  by  the 
solid  metal.  After  the  porcelain  part  of  the  crown  of  the 
lateral  incisor  had  been  fitted  to  the  model  and  soldered  to 
the.  wire — this  portion  of  the  wire  should  be  flattened  some- 
what in  some  cases — the  groove  was  made  around  the  porce- 
lain ;  the  foil  was  solidly  built  in  place,  and  finished  in  the 
manner  hereinbefore  described,  the  crown  was  then  inserted 
and  the  contour  of  the  cuspid  tooth  was  restored  with  gold. 
The  root  of  the  left  central  incisor  remains,  and  the  crown 
which  is  fitted  upon  it  is  prepared  for  the  building  on  of  gold 
foil ;  after  which  it  will  be  ready  for  insertion.*  When  this 
crown  is  put  in  place,  the  gold  wire  is  to  be  surrounded  with 
gutta-percha ;  but  little  of  which  is,  or  should  be,  needed  in  the 
pulp-chamber,  because  of  the  close  fitting  of  the  wire  in  and  of 
the  crown  upon  the  root.  During  this  preparation,  a  plain  '  pivot ' 
crown  is  kept  upon  the  root,  held  by  wood  and  gutta-percha. 

*  The  groove  is  not  distinctly  shown  in  the  cut  (Fig.  351). — M.  H.  W. 


300  MECHANICAL    DENTISTRY. 

"  When  the  lateral  incisor  crown,  in  the  case  illustrated,  was 
ready  for  insertion,  and  the  gold  at  the  base,  which  was  to  rest 
upon  the  gum,  had  been  nicely  fitted  to  it,  and  the  whole  of 
the  gold  was  smoothly  finished,  a  good-sized  piece  of  medium 
rubber-dam  was  applied  to  the  teeth  (the  cuspid  and  the  central 
and  lateral  incisors)  on  each  side  of  the  space  to  be  filled,  and 
arranged  so  as  to  cover  the  gum  and  the  root  between  these 
teeth.  The  crown  was  made  to  so  rest  upon  the  gum  as  to  press 
the  blood  from  the  capillaries  of  the  part,  and  thus  prevent 
particles  of  food  from  getting  under  it.  (While  the  thickness  of 
the  rubber-dam  might,  to  some  extent,  prevent  the  placing  of 
such  a  crown  against  the  gum  as  firmly  as  it  should  be  pressed, 
yet  this  thickness  is  compensated  for  by  the  pressing  up  of  the 
gum  when  the  floss-silk  ligatures  are  placed  about  the  neck  of 
each  adjoining  tooth.)  After  all  this  had  been  done,  and  fine 
barbs  were  cut  around  the  gold  wire  with  a  sharp  knife-blade, 
oxychlorid  of  zinc  was  placed  in  the  pulp-chamber  of  the 
cuspid  tooth,  and,  while  the  cement  was  still  plastic,  the  crown 
was  at  once  pressed  to  place,  and  held  there  for  a  few  moments. 

"After  the  cement  had  hardened  sufficiently  to  safely  admit 
of  it,  it  was  cut  away  from  around  the  wire  at  such  parts 
as  would  make  proper  anchorage  for  the  gold.  There  was, 
and  in  every  case  should  be,  a  little  space  left  between  the 
wire  and  cervical  wall  to  be  filled  with  gold  for  the  protection 
of  the  enamel  at  this  part.  Narrow  pieces  of  light  cohesive 
foil  were  first  placed  in  this  space  with  small,  suitably  curved 
instruments,  and  afterwards  solidified  with  the  mallet ;  after 
which  a  little  larger  (though  still  narrow)  and  heavier  (none 
over  No.  32)  pieces  of  folded  foil  were  used  for  placing  around 
and  about  the  wire  in  the  root,  filling  the  cavity,  restoring 
the  contour,  covering  and  protecting  the  prepared  margins  of 
enamel,  each  piece  of  the  gold  being  thoroughly  cohesive  and 
made  compact  with  the  electro-magnetic  mallet.  The  surface  of 
the  gold  placed  around  the  wire  between  it  and  the  cervical  wall, 
as  well  as  all  that  part  near  the  gum,  was  smoothly  finished  with 
small  files  and  very  narrow  (y^g-inch  wide)  strips  of  emery  cloth 
before  the  removal  of  the  rubber-dam  ;  after  which  the  remain- 
der of  the  ofold  was  made  smooth  and  so  trimmed  down  as  to  be 


BRIDGE-DENTURES.  3OI 

sure  of  the  proper  occlusion  of  the  teeth.  The  crown  attached 
to  the  cuspid  tooth  was  made  just  short  enough  to  be  free  from 
the  striking  of  the  lower  teeth.  The  operation  was  finished  at 
another  time  with  Hindostan  stones,  together  with  pumice  upon 
fine  wood  made  into  suitable  shape. 

"  When  a  crown  can  be  securely  attached  to  one  instead  of 
two  teeth,  the  time  of  building-in  is  lessened  about  one-half. 
The  slight  movement  which  takes  place  in  the  socket  of  the 
tooth  supporting  the  crown  is  not  so  interfered  with  as  when  two 
teeth  are  fixed  together  by  the  gold  wire  holding  the  porcelain. 
If  it  should  afterwards  become  necessary  to  perform  operations 
upon  the  adjoining  teeth,  the  rubber-dam  can  as  readily  be 
applied  as  before  attaching  the  crown." 

Dr.  Darby's  Method. — Professor  E.  T.  Darby,  in  commenting 
on  the  method  just  described,  says  :  "  Dr.  B.  J.  Bing  was  the  first 
to  call  my  attention  to  a  method  of  building  one  tooth  into  the 
adjoining  teeth  by  means  of  gold  wires  running  from  the  artificial 
into  the  natural  teeth.  I  have  never  seen  any  of  Dr.  Bing's 
operations,  but  Dr.  Marshall  H.  Webb  has  called  my  attention 
to  one  or  more  in  the  mouths  of  his  patients,  which  have  done 
good  service  for  years.  I  also  have  in  my  own  practice  several 
which  have  proved  most  satisfactory. 

"The  cuts,  Figs.  352  and  353,  represent  two  cases  where  arti- 
ficial crowns  have  received  their  support  from  the  adjoining 
teeth.  It  is  desirable  to  have  a  pulpless  tooth  for  a  neighbor, 
though  I  question  if  one  would  be  justified  in  devitalizing  a  pulp 
to  secure  this  end.  In  the  cases  presented,  a  piece  of  gold  wire 
was  soldered  to  the  backing  of  the  porcelain  tooth,  and  allowed 
to  extend  well  up  the  pulp-canal  of  one  of  the  adjoining  teeth. 
After  it  had  been  nicely  fitted  to  its  place,  the  rubber-dam  was 
applied  and  drawn  tightly  over  the  gum  between  the  two  natu- 
ral teeth  ;  the  canal  of  the  devitalized  tooth  was  then  filled  with 
oxychlorid  of  zinc  and  the  tooth  with  its  gold  support  pressed 
into  position.  When  the  cement  had  hardened,  the  bulk  of  it 
was  cut  out  and  the  space  filled  thoroughly  with  gold.  The  other 
end  of  the  bar  was  packed  around  with  gold  foil,  and  the  cavity 
of  decay  or  cavity  of  convenience  was  filled  in  the  ordinary  way. 

"  It  is  always  better  to  take  an  impression  of  the  space  and 


302 


MECHANICAL    DENTISTRY, 


adjoining  teeth  at  the  outset,  and  then  do  the  major  part  of  the 
work  in  the  laboratory.  The  gold  wire  which  enters  the  root 
can  be  bent  or  shaped  with  the  pHers  when  the  crown  is 
adjusted  for  final  insertion. 

"  I  would  not  be  understood  as  saying  that  these  operations 
can  only  be  performed  successfully  where  there  is  a  devitalized 
tooth  for  a  neighbor  ;  on  the  contrary,  I  have  seen  teeth  inserted 


in  this  way  where  both  teeth  were  living,  but  the  support  which 
is  to  be  derived  from  the  long  right  angle  of  gold  in  the  root  is 
certainly  a  great  security  against  accident,  adding,  as  it  must, 
much  strength  to  the  operation." 

The  Plate  and  Pin  Bridge. — Professor  Wilbur  F.  Litch  has 
greatly  improved  and  simplified  the  method  of  attaching  a  single 
crown  to  the  adjoining  teeth  in  the  class  of  cases  under  consider- 
ation.    The  following  is  his  description  of  the  process  : — 

Fig.  353. 


"  Fig.  354  represents  a  typical  case,  in  which  a  lateral  incisor 
(crown  and  root)  has  been  lost,  the  cuspid  and  front  incisor,  fully 
vitalized,  and  without  approximal  carious  cavities,  remaining  in 
position. 

"  I.  Take  in  plaster  an  accurate  impression  of  the  cuspid  and 
incisor  and  the  interspace.  From  this  obtain  a  plaster  model  of 
the  parts. 


BRIDGE-DENTURES. 


j^6 


"  2.  Make  from  pure  gold,  rolled  to  the  thinness  of  26,  standard 
gauge,  base-plates,  to  be  carefully  adjusted  to  the  palato-approxi- 
mal  surfaces  of  the  cuspid  and  incisor.  These  can  be  made  by 
swaging  on  dies  and  counter-dies  obtained  from  the  model,  but 
more  conveniently  by  bending  the  gold  into  shape  upon  the 
plaster  model  and  pressing  and  burnishing  it  into  perfect  adap- 
tation upon  the  natural  teeth. 

"  3.  Select  a  plain  plate  porcelain  tooth  of  suitable  length, 
shape,  and  shade,  and  wide  enough  to  fit  easily  into  the  inter- 
space.    Let  the  neck  of  the  tooth  rest  lightly  upon  the  gum. 

"  4.  With  pure  gold  or  platinum  make  a  backing  for  the  porce- 
lain tooth. 

"  5.  Place  the  tooth  thus  prepared  and  the  base-plates  already 
made  upon  the  cast,  and  accurately  adjust  the  approximal  edges 

Fig.  354. 


of  the  base-plates  to  the  backing  of  the   porcelain   tooth  in  situ 
upon  the  cast. 

"  6.  When  this  adjustment  is  made,  cement  together  the  base- 
plates and  backing  with  a  brittle,  resinous  cement  (resin,  two 
parts  ;  wax,  one  part ;  or  sealing-wax  will  answer),  and  before 
the  cement  has  fully  hardened  remove  from  the  cast  to  position 
in  the  mouth,  perfecting  the  final  adjustment  there.  By  this 
method  much  greater  accuracy  of  adaptation  is  obtained,  as  the 
lines  of  length,  width,  and  contour  are  too  fine  to  be  reproduced 
with  absolute  fidelity  in  a  plaster  model.  In  this  part  of  the  pro- 
cess too  much  care  cannot  be  taken  to  have  each  piece  of  the 
appliance  fitted  with  absolute  accuracy  to  the  surface  for  which 
it  is  designed.  When  this  has  been  accomplished,  throw  upon 
the  yet  more  or  less  plastic  cement  a  stream  of  ice-cold  water 
from  an  office  syringe  ;  this  renders  the  cement  perfectly  brittle 


304  MECHANICAL    DENTISTRY, 

and  incapable  of  bending.  Immediately  remove  from  the 
mouth  and  invest  in  a  mixture  of  equal  parts  of  marble  dust 
and  plaster-of- Paris. 

"  7.  After  the  investment  has  firmly  set,  solder  the  base-plates 
to  the  backing,  and  the  backing  to  the  platinum  pins  of  the 
porcelain  tooth,  using  as  a  solder  20-carat  gold.  Thus  joined, 
the  appliance  will  present  the  appearance  shown  in  Fig.  358 — A 
representing  the  base-plate  for  the  cuspid  ;  B,  the  base-plate  for 
the  incisor ;  C,  the  porcelain  tooth  with  its  platinum  backing  ; 
D,  the  points  of  union  between  the  base-plates  and  backing. 
At  these  points  the  greatest  strength  is  required,  and  it  is  impor- 
tant that  here  a  large  amount  of  the  solder  should  be  placed. 
The  porcelain  tooth  being  usually  thinner  than  the  natural  teeth, 
there  is  nearly  always  an  angle  or  depression  at  the  points  indi- 
cated, in  which  the  thickness  of  the  gold  can  be  considerably 
increased  without  interfering  with  occlusion. 

"  8.  For  the  purpose  of  attaching  the  denture  as  thus  far  con- 
structed, drill  a  small  cylindrical  opening  through  the  palatal  sur- 
face of  the  enamel  of  the  cuspid  and  incisor  respectively.  These 
openings  should  usually  be  placed  about  as  indicated  in  Fig.  357, 
at  C.  D.  Sometimes,  owing  to  a  close  occlusion,  or  to  the  con- 
tour of  the  tooth,  it  is  desirable  that  they  should  be  located  a 
trifle  nearer  the  neck  of  the  tooth.  Each  opening  should  be 
well  undercut,  but  must  not  encroach  upon  the  dentine  far  enough 
to  endanger  the  pulp.  In  size  the  openings  need  not  be  larger 
than  will  admit  a  platinum  pinhead,  in  diameter  corresponding 
to  13,  standard  gauge,  with  a  shank  of  18,  standard  gauge. 
Into  each  of  these  openings  must  be  fitted  a  platinum  pin  of  the 
size  indicated.  The  head  of  each  pin  must  be  made  thin  and 
perfectly  flat  both  upon  its  upper  and  under  surfaces. 

"  9.  In  each  of  the  base-plates  make  an  opening  correspond- 
ing in  position  to  those  in  the  natural  teeth.  Pass  through  these 
openings  and  cement  in  them  the  free  ends  of  the  platinum  pins. 
While  the  cement  is  yet  plastic,  place  the  denture  in  position  in 
the  mouth,  carefully  pressing  the  pin-heads  into  the  openings 
made  for  them  and  burnishing  the  base-plates  into  perfect  con- 
tact with  the  palatal  surfaces  of  the  teeth ;  chill  the  cement,  remove 
and  invest  as  before,  and  with  20-carat  gold  solder  the  pins  to 


BRIDGE-DENTURES. 


305 


the  base-plates,  flowing  upon  them  and  the  backing-  as  much  of 
the  solder  as  may  be  necessary  to  give  them  the  desired  thick- 
ness and  rigidity  ;  the  amount  admissible  largely  depending  upon 
the  nature  of  the  occlusion,  a  central  thickness  of  about  21, 
standard  gauge,  being  all  that  is  really  requisite  for  strength, 
while  the  edges  can  be  made  much  thinner. 

"  Fig-  355  represents  the  appliance  without  the  pin.     A  is  the 


Fig.  355. 


Fig.  356. 


porcelain  tooth  and  backing  ;  E,  the  base-plates  ;  C  and  F,  the 
openings  for  the  pins. 

"  Fig.  356  represents  the  appliance  completed  with  the  pins  in 
position. 

"  F'g-  357  represents  the  natural  teeth  and  interspace  B,  with 
openings  for  retaining-pins,  C  D. 


Fig.  357. 


"  Fig.  358,  already  described,  represents  the  appearance  pre- 
sented when  the  bridge  is  cemented  in  position. 

"  To  Attach  the  Bridge. — To  attach  the  bridge  the  best  attain- 
able oxyphosphate  cement  should  be  used.  It  is  desirable  that 
it  should  set  slowly.  Thoroughly  dry  the  teeth  and  denture  ; 
mix  the  cement  to  as  thick  a  consistency  as  is  compatible  with 
perfect  plasticity.  A  thick,  viscid,  semi-fluid  mass  is  what  is 
20 


06  MECHANICAL    DENTISTRY. 


required.  With  suitable  instruments,  swiftly  but  carefully  place 
the  cement  around  the  head  and  shank  of  each  platinum  pin, 
and  also  in  the  openings  in  the  natural  teeth.  This  care  is  neces- 
sary in  order  to  exclude  all  the  air-bubbles  and  thoroughly 
engage  the  pin-heads  in  the  cement.  They  furnish  ample  retain- 
ing surface,  but  none  to  spare.  In  packing  the  cement  around 
the  pins,  the  under  surface  of  the  base-plates  should  at  the  same 
time  be  covered. 

"  The  above  details  being  perfected,  the  denture  is  at  once 
carried  to  position,  and  with  broad-pointed,  serrated  instruments 
pressed  firmly  into  place,  the  excess  of  cement,  if  of  the  proper 
consistency,  freely  oozing  at  all  margins. 

"  Too  much  care  cannot  be  exercised  in  the  cementing  pro- 
cess. As  every  second  of  time  is  of  value,  all  instruments  re- 
quired must  be  selected  and  conveniently  placed  before  the 
oxyphosphate  is  mixed.  To  secure  the  most  rapid,  and 
at  the  same  time  thorough,  admixture  of  the  phosphoric 
acid  and  zinc  oxid,  a  thick  plate-glass  slab,  four  inches  square, 
with  a  flat  (not  a  concave)  surface  should  be  used.  The  spatula 
should  be  of  steel,  thin  and  elastic,  and  six-tenths  of  an  inch 
wide.  With  these  implements  the  whole  mass  of  cement,  acid, 
and  oxid  can  almost  instantly  be  brought  into  union,  the  spatula 
being  used  as  a  muller.  When  a  narrow  and  rigid  spatula  is 
used  in  mixing  any  considerable  amount  of  oxyphosphate,  the 
process  can  be  accomplished  only  in  detail,  portion  by  portion, 
much  valuable  time  being  thus  lost,  during  which  the  setting  pro- 
cess is  every  moment  hastening  to  its  completion  and  rendering 
the  cement  unfit  for  use  in  this  or  any  other  form  of  bridge-work. 
A  large  excess  of  acid  will,  of  course,  make  a  thinner  and  more 
slowly-setting  mass,  but  a  cement  thus  mixed  is  deficient  in 
strength  and  too  unstable  to  give  good  results. 

"  A  very  troublesome  obstacle  to  success  in  the  use  of  the 
oxyphosphate  cements  will  often  be  found  in  the  temperature  of 
the  air,  an  elevated  temperature  so  hastening  those  chemical 
changes  upon  which  the  hardening  of  these  cements  depends  as 
to  render  their  use  almost  impracticable.  This  difficulty  is 
likely  to  occur  only  in  the  hotter  seasons  of  the  year,  and  can 
readily  be  overcome  by  placing  the  mixing-slab,  as   well  as  the 


BRIDGE-DENTURES.  30/ 

acid  and  oxid   bottles,  in  cold  water  until  their  temperature  has 
been  considerably  reduced. 

"  During  severe  winter  weather  too  low  a  temperature  also 
gives  trouble,  the  acid  and  oxid,  even  when  the  former  is  in 
some  excess,  forming  a  powdery  mass  utterly  unworkable,  but 
which  melts  down  into  an  almost  fluid  condition  when  brought 
into  contact  with  the  warmth  of  a  tooth  in  situ.  A  temperature 
between  60°  and  65°  F.  secures  the  best  results  in  mixing  oxy- 
phosphate  cements. 

"  Application  to  Pidplcss  Teeth. — In  the  above  description  the 
vitality  of  the  cuspid  and  incisor  has  been  assumed  ;  but,  as  can 
readily  be  understood,  the  pin  and  plate  bridge  can  be  even  more 
readily  and  securely  placed  when  one  or  both  pulps  are  devital- 
ized, for  the  reason  that,  the  pulp-chamber  being  empty,  the  pin- 
holes in  that  tooth  can  be  made  as  much  larger  and  deeper  as 
may  be  deemed  desirable,  the  size  of  the  pin  being,  of  course, 
correspondingly  increased.  In  a  devitalized  tooth,  too,  the  base- 
plate can  be  sunk  into  the  palatine  surfaces  when  they  interfere 
with  occlusion,  as  sometimes  happens  when  the  antagonism  of 
the  lower  teeth  is  very  close  and  the  overlap  is  considerable. 

"  Ordinarily,  however,  such  interference  is  inconsiderable,  and 
the  difficulty  can  always  be  overcome  either  in  devitalized  teeth 
by  the  expedient  just  suggested,  or  by  carrying  the  base-plates 
as  far  away  from  the  cutting-edge  as  practicable,  at  the  same 
time  making  them  at  the  point  of  contact  as  thin  as  is  consist- 
ent with  strength  ;  finally,  if  necessary,  removing  a  slight  por- 
tion of  the  cutting-edge  of  the  occluding  lower  tooth. 

"  As  experience  with  this  as  well  as  other  forms  of  bridge- 
work  has  fully  demonstrated,  a  slight  mutilation  of  a  natural 
tooth  is  far  less  destructive  in  its  ultimate  results  than  is  the 
wearing  of  partial  plates,  in  the  use  of  which  pressure  falls  upon 
the  gum  tissue,  with  the  ultimate  effect  of  stripping  it  from 
around  the  necks  of  the  natural  teeth,  thus  denuding  them  of 
that  protective  covering,  and  exposing  them  to  the  ravages  of 
decay,  and  it  may  be  safely  affirmed  that  in  all  applicable  cases 
the  pin  and  plate  bridge  accomplishes  its  purpose  with  the 
minimum  of  injury  to  the  natural  organs. 

"  The  small  size  of  the  retaining-pins  may  excite  doubts  as  to 


308  MECHANICAL    DENTISTRY. 

the  strength  of  the  denture  ;  but  pins  smaller  in  size  are  con- 
stantly used  for  attaching  porcelain  teeth  to  plates,  and  in  the 
upper  incisors  these  pins  are  much  less  advantageously  placed 
for  resistance  to  pressure  than  are  those  embedded  in  the  natural 
teeth  in  the  process  above  described. 

"  The  weakest  point  in  the  bridge  is  not  the  pins,  but  the 
cement ;  this,  while  not  so  strong  as  the  fused  porcelain  which 
surrounds  the  pins  in  artificial  teeth,  is,  as  experience  has 
demonstrated,  just  strong  enough  to  resist  all  ordinary  wear  and 
tear,  without  being  so  intractable  as  to  render  the  removal  of 
the  denture  for  purposes  of  repair  a  practical  impossibility  by 
any  method  short  of  its  destruction. 

"  Even  with  a  good  oxyphosphate  cement,  the  work  of  re- 
moval is  one  of  no  slight  difficulty,  and  requires  the  exercise  of 
so  considerable  an  amount  of  force  that  no  one  who  has  had 
occasion  to  perform  that  operation  will  question  the  security  of 
any  well-constructed  specimen  of  this  form  of  bridge.  During 
an  experience  of  some  seven  or  eight  years  in  their  use,  the 
writer  has  had  but  one  or  two  cases  in  which  the  appliance  be- 
came loosened,  and  only  one  in  which  it  was  detached  outright. 
In  the  latter  case  the  bridge  (constructed  with  the  natural  tooth 
of  the  wearer  instead  of  a  porcelain  substitute)  had  been  firmly 
in  position  for  more  than  a  year,  when  the  sudden  wrench  conse- 
quent upon  biting  into  a  very  hard  peach  detached  it.  Being 
immediately  replaced,  it  has  since  then  (some  two  years  ago) 
done  good  service.  In  such  cases  it  is  usually  advisable 
to  slightly  deepen  the  undercuts  in  the  pin-holes  before  re- 
placing. 

"  Repairing. — As  in  all  other  forms  of  bridge-work  in  which 
porcelain  teeth  are  used,  the  accident  most  likely  to  happen  is 
the  fracture  of  this  brittle  material.  As  the  bridge  does  not 
yield  under  pressure  as  does  a  detached  plate  resting  upon  the 
compressible  gum-tissue,  this  form  of  breakage  is  one  to  which 
bridge-work  is  more  than  usually  liable.  For  the  pin  and  plate 
bridge  the  least  difficult  method  of  repair  is  to  separate  the  tooth 
and  backing  from  the  base-plates  by  means  of  a  watch-spring 
saw,  and  then  force  off  the  base-plates  singly,  this  being  much 
more  easily  accomplished  than  their  removal  when  united  to  the 


BRIDGE-DENTURES. 


309 


backing.  Another  tooth  is  then  selected,  fitted,  backed,  and 
soldered  as  before. 

"  As  a  rule,  the  writer  has  confined  the  use  of  this  form  of 
bridge  to  cases  in  which  only  a  single  incisor  is  missing,  but  he 
has  successfully  attached  a  front  and  lateral  incisor  to  a  cuspid 
and  the  remaining  front  incisor.  When  an  unusual  strain  is  to 
be  expected,  the  retaining-pins  and  pin-holes  should,  when 
practicable,  be  made  correspondingly  large,  or  two  smaller  pins 
may  be  anchored  in  one  tooth,  which  latter  plan  gives  very  great 
resisting  power  and  renders  removal  in  the  highest  degree 
difficult  and  laborious. 

•'  Porcelain  Tips. — Figs.  359,  360,  and  361  show  how  the  pin 
and  plate  process  may  be  utilized  for  the  attachment  of  porce- 
lain tips  for  broken  or  decayed  incisors  when  the   appearance 


Fig.  359. 


''^<1  ^J 


^^^  I 


Fig.  ^61. 


of  gold  fillings  is  obnoxious  to  the  patient.  A  represents  the 
porcelain  tips  ;  B,  the  space  to  be  filled  by  them  ;  C  and  D,  the 
opening  for  retaining-pins  ;  F  and  G,  openings  in  the  base-plates 
(E)  for  the  pins.  Fig.  361  shows  the  appliance  with  pins  at- 
tached." 

The  following  are  descriptions  of  methods  of  replacement 
known  as  "  Bridge-Work  "  proper,  which  is  but  an  extension  or 
amplification  of  the  principles  involved  in  the  construction  and 
application  of  the  pieces  just  considered. 

Dr.  Dexter,  in  defining  this  method  of  substitution,  says : — 
"The  main  principles  of  bridging  are,  broadly,  to  permanently 
place  artificial  teeth  between  remaining  natural  teeth  and  roots 
in  such  manner  that  the  porcelain  substitutes  shall  fill  the  spaces 
made  vacant  by  nature,  while  resting  upon  and  being  held  in 
place   by  the  natural   teeth  ;  the  porcelain   teeth,  in   the  older 


3IO 


MECHANICAL    DENTISTRY. 


methods,  resting  with  more  or  less  pressure  upon  the  gum,  and 
in  later  methods  being  raised  quite  clear  of  the  gum  and  sup- 
ported by  the  natural  teeth  or  roots  in  the  same  manner  that 
a  bridge  truss  or  floor  rests  upon  its  piers — hence  the  name 
given  the  operation." 

Fig.  ^62. 


Under  this  head  may  properly  be  classed  a  process  of  replace- 
ment described  by  Prof.  Litch  in  connection  with  the  "  pin  and 
plate  attachments  "  as  a  means  of  support  for  single  front  teeth, 
a  method  of  attachment  which,  he  says,  although  chiefly  applicable 
to  the  incisors,  may  be  combined  with  crown  or  bar  bridges  for 
molars  and  bicuspids.  The  following  descriptions  by  Prof.  Litch 
relate  to  a  case  in  illustration  of  the  special  method  of  attach- 
ment spoken  of: — 

Fig.  363. 


"  Fig.  362  represents  a  practical  case  in  which  the  upper  third 
molar  and  first  bicuspid  (both  without  antagonizing  teeth)  were 
utilized  for  the  attachment  of  a  bridge  made  of  gold  crowns  with 
porcelain  facings,  to  supply  the  loss  of  the  intervening  teeth. 

"  Fig.  363  represents  the  case  as  prepared  for  the  bridge.     A, 


BRIDGE-DENTURES.  3II 

the  inner  cusp  of  the  bicuspid  cut  down  to  allow  the  placing  of 
a  sufficiently  thick  crown-plate  ;  B,  a  cylindrical  undercut  open- 
ing between  the  cusps  for  a  retaining-pin  ;  C,  the  third  molar 
made  uniform  in  size  from  neck  to  grinding  surface,  the  latter 
also  being  considerably  retrenched  ;  D,  the  crown-plate  of  a 
partial  cap,  made  of  pure  gold,  soldered  with  20-carat  gold,  and 
so  constructed  as  to  cover  every  portion  of  the  tooth  except  its 
buccal  surface,  the  free  edge  passing  up  under  the  gum  ;  E,  a 
retaining-pin  adapted  to  the  opening  B  ;  F,  the  gold  cap  for  the 
molar. 

"  Fig.  364  represents  the  bridge  anchored  in  position  with 
oxyphosphate  cement. 

"  In  the  above  case  it  will  be  observed  that  there  is  a  consider- 
able space  between  the  bicuspid  and  cuspid.  .  This  made  it  readily 

Fig.  364. 


practicable  to  give  so  considerable  a  thickness  to  the  mesial  wall 
of  the  partial  cap  as  to  hold  it  securely  against  the  side  of  the 
tooth.  Had  the  space  been  less,  contact  with  the  cuspid  would 
have  afforded  the  desired  security. 

"  Fig.  365  represents  another  case  in  which  a  bridge  was  at- 
tached by  a  bar,  partial  cap,  and  retaining-pin.  A  is  an  upper 
second  bicuspid  (without  antagonist) ;  B,  its  inner  cusp  cut 
down;  C,  opening  for  retaining-pin  ;  D,  second  molar,  with  slot 
for  bar ;  E,  cuspid  ;  F  represents  the  partial  facing  ;  G,  the  re- 
taining-pin ;  H,  a  molar  crown  of  gold,  with  porcelain  front;  I, 
a  platinum  bar  attached  to  the  crown  (H)  and  made  to  fit  into  a 
slot  (at  D) ;  J,  a  plain  plate  cuspid,  heavily  backed  and  strongly 
soldered  to  the  partial  cap,  but  left  without  attachment  to  or 
contact  with  the  cuspid. 


312 


MECHANICAL    DENTISTRY. 


"  Fig.  366  shows  the  bridge  anchored  in  position. 

"  This  case,  after  two  years  of  wear,  is  still  in  perfect  condition 

and  doing  good  service.     As  it  was  possible  to  keep  the  gold 

attachments,  backings,  etc.,  out  of  sight,  the  appearance  presented 

is  very  natural. 

Fig.  365. 

F 


"The  bridge  shown  in  Fig.  364  has  been  in  use  but  a  few 
months. 

"The  absence  of  antagonizing  teeth  for  the  bicuspids  in  each  of 
these  cases  was  a  favorable  condition,  as  a  considerable  thickness 
could  be  given  to  the  crown-plate  without  any  interference  with 
occlusion.  When  the  conditions  are  not  so  favorable,  cutting 
down  the  inner  cusp  to  the  required  extent  and    sinking  the 

Fig.  366. 


opening  for  the  retaining-pin  to  the  necessary  depth  are  processes 
certainly  to  be,  as  a  rule,  preferred  to  the  entire  removal  of  the 
crown  for  the  purpose  of  ferruling  the  root  for  the  mounting  of 
a  crown  of  gold  and  porcelain — a  procedure,  however,  not  by 
any  means  to  be  indiscriminately  denounced,  for  in  many  cases 
it  is  in  the  highest  degree  advisable. 


BRIDGE-DENTURES.  313 

"  There  is  this  fact  to  be  considered  in  regard  to  the  use  of  the 
partial  caps  here  figured — that  many  patients  can  be  induced  to 
consent  to  their  employment  who  would  refuse  to  submit  to  more 
radical  measures,  and  thus,  even  when  the  latter  would  be  advis- 
able, the  former  may  be  employed  as  a  compromise,  or  even  as 
a  temporary  expedient.  Having  once  tested  the  advantage  of  a 
well-fitting  bridge,  the  w^earer  is  much  more  hkely  to  consent  to 
whatever  measures  are  necessary  to  give  it  security  and  per- 
manence. 

"  In  the  cases  figured,  however,  as  well  as  in  analogous  cases, 
these  qualities  seem  to  be  amply  secured.  In  every  instance  in 
which  the  removal  of  a  pin  and  plate  bridge  has  been  necessary, 
the  film  of  oxyphosphate  cement  has  been  found  intact,  and  the 
surface  of  the  tooth  upon  which  it  rested  perfectly  protected  from 
decay.  The  only  exceptions  to  this  rule  have  been  the  very  few 
cases  in  which  one  or  the  other  of  the  retaining-pins  has  become 
loosened,  the  bridge  being  for  some  weeks  still  worn  in  the 
loosened  condition.  Under  such  circumstances  the  cement  will, 
of  course,  become  detached  and  wash  out,  admitting  food  and 
secretions  ;  but  so  long  as  the  appliance  remains  immobile — and 
that  is  its  normal  state — the  cement  rests  undisturbed.  It  need 
hardly  be  claimed  that  its  durability  is  without  limit,  although 
under  a  metallic  covering  it  appears  to  be  practically  so ;  but  under 
the  conditions  represented  in  the  processes  as  above  described, 
it  is  certainly  good  for  many  years  of  satisfactory  service,  and 
when  it  fails,  through  chemical  abrasion,  it  will  fail  first  at  the 
free  margins,  where  defects  are  most  easily  seen  and  remedied." 

Dr.  Register's  Method. — The  following  is  a  condensed  ac- 
count, by  Dr.  Dexter,  of  a  method  of  bridging  devised  by  Dr.  H. 
C.  Register,  one  of  the  earliest  experimenters  in  this  method  of 
replacement.  The  distinctive  feature,  as  also  the  special  merit, 
of  Dr.  Register's  appliance  consists  in  the  provision  made  for 
the  ready  replacement  of  broken  crowns.  The  process  is  thus 
described : — 

"Taking  a  typical  case  (Fig.  367),  a  rim  or  saddle  of  gold, 
platinum,  or  iridinized  platinum  is  struck  to  fit  the  spaces  between 
the  teeth  A  and  B.  To  this  are  attached  bars  X  (Fig.  369),  to 
enter  the  fillings  at  Z,  Z  (Fig.   368).     Posts  or  pivots  (D,  Fig. 


.14 


MECHANICAL    DENTISTRY. 


369)  are  soldered  upon  this  saddle  where  the  artificial  teeth  are 
to  be  placed,  their  free  ends  being  threaded  to  carry  the  nut  E. 


li'aili.wii 

Fig.  368. 


l;mi«i!||!ril[iitl'[l|||!l|;  \ 


.    z 


E 


Fig.  369. 


Hollow  crowns,  countersunk  for  the  nut  at  G,  and  having  the 
necks  ground  to  reach  over  the  saddle  and  press  upon  the  gum, 


BRIDGE-DENTURES.  3  I  5 

are  fitted  over  each  post.  Amalgam  is  used  to  fill  in  the  space 
between  the  post  and  the  tooth-wall,  as  in  a  Bonwill  setting,  and 
the  crowns  are  drawn  to  place  and  held  with  the  nut.  The 
saddle  is  fixed  in  its  place  in  the  mouth,  before  the  crowns  are 
finally  attached,  by  filling  into  the  cavities  Zthe  bars  X,  X." 

Dr.  Williams'  Method. — Dr.  J.  L.  Williams,  of  New  Haven, 
Conn.,  has  given  to  the  profession  a  number  of  important  com- 
munications relating  to  bridge-work,  to  which  space  is  given  to 
such  portions  only  as  relate  more  especially  to  practical  details. 
The  initial  portion  of  the  following,  reproduced  from  the  Dental 
Cosmos,  treats  also  of  single  crown  replacement,  and  is  embodied 
in  this  connection  as  having  immediate  and  necessary  relation  to 
subsequent  descriptions. 

The  following  are  Dr.  Williams'  descriptions  of  his  methods 
of  crown  and  bridge  replacement. 

"  As  the  single  crown  is  the  beginning  and  end  of  all  bridge- 
work,  a  description  of  that  particular  form  which  is  of  the  great- 
est practical  value  in  this  work  will  first  be  necessary.  This  is 
known  as  the  Richmond  Crown,  although  not  the  crown  which 
Dr.  Richmond  claims  as  his  invention.  It  consists  essentially 
of  three  parts:  a  square  pin  of  platinum  and  iridium  which  enters 
the  enlarged  pulp-canal,  a  cap  of  gold,  and  the  porcelain  face, 
which  is  the  ordinary  plate  tooth. 

"  This  crown  is  made  in  the  following  manner  :  After  the  end 
of  the  root  is  made  perfectly  smooth  with  corundum  wheels  and 
properly-shaped  scalers,  a  gold  ferrule  or  band  is  fitted  around 
it.  If  it  is  desirable  that  this  band  should  be  entirely  concealed, 
the  labial  surface  of  the  root  should  be  beveled  a  little  above 
the  margin  of  the  gum,  and  after  the  band  has  been  soldered  it 
may  be  placed  in  position,  and  the  line  of  contour  of  the  margin 
of  the  gum  marked  upon  the  front  of  the  band.  The  proper 
bevel  can  then  be  cut  and  the  edges  squared  upon  a  corundum 
wheel,  leaving  the  lingual  portion  of  the  band  a  little  longer  than 
the  front.  Pure  gold,  rolled  to  No.  34  of  the  standard  gauge 
(American),  is  used  for  soldering  upon  the  beveled  surfaces, 
thus  making  a  closed  cap  for  the  end  of  the  root.  A  suitable 
tooth  is  now  selected  and  backed  with  pure  platinum  or  pure 
eold.      The   cervical   end  of  the  tooth   is  then   ground  to  the 


3i6 


MECHANICAL    DENTISTRY. 


proper  position  on  the  front  bevel  of  the  cap,  all'  of  the  fitting 
being  done  while  the  cap  is  in  position  on  the  root. 

"  After  the  fitting  is  completed,  the  cap  is  removed,  and  the 
tooth  attached  by  strong  resin  wax  and  again  placed  in  position 
while  the  wax  is  warm.     Any  slight  change  in  position  which 


Fig.  370. 


is  necessary  can  then  be  easily  made.  The  tooth  and  cap  are 
now  removed  together,  invested,  and  united  at  the  back  by 
solder.  It  is  well  to  use  a  solder  for  the  cap  with  a  higher 
melting-point  than  that  used  for  the  backing,  as  it  obviates  the 


danger  of  unsoldering  the  band  when  the  backing  is  flowed  on. 
After  finishing  and  polishing  the  work,  the  end  of  the  root  is 
made  perfectly  dry,  a  sufficient  quantity  of  oxyphosphate  cement, 
mixed  somewhat  thinner  than  for  filling  purposes,  is  placed  in 
the  enlarged  pulp-canal  and  also  in  the  cap.     The  crown  is  then 


BRIDGE-DENTURES. 


317 


carried  to  the  place  with  firm,  steady  pressure,  and  held  a  few 
minutes  until  the  cement  is  sufficiently  hard  to  prevent  displace- 
ment. The  surplus  cement  which  has  oozed  out  around  the 
band  should  be  carefully  removed  and  the  work  is  then  com- 
pleted.    This  is  all  illustrated  in  Fig.  370. 

"  The  bridge-work  is  simply  an  extension  of  the  crowns  over 
spaces  where  the  natural  teeth  have  been  lost. 

"  ^^S-  371  ^^'^^  drawn  from  a  model  of  a  case  in  practice.  In 
this  the  roots  of  the  centrals  are  shown  prepared  for  the  fitting 
of  the  bands,  the  laterals  having  been  extracted.  Single 
crowns  are  made  for  these  roots  precisely  as  described.  They 
are  then  temporarily  placed  in  position.  Laterals  are  selected, 
backed,  ground,  and  fitted  to  position.  The  laterals  are  then 
attached  by  means  of  strong  wax  to  the  centrals,  carefully  ad- 

FiG.  373. 


justed  in  the  position  which  we  wish  them  to  occupy,  and  the 
whole  removed  in  an  impression  of  investing  material.  An  ad- 
ditional quantity  of  investment  is  mixed  and  poured  over  the 
exposed  ends  of  the  caps,  and  the  whole  allowed  to  harden,  after 
which  the  investing  material  is  cut  away  from  the  backs  of  the 
teeth  and  crowns,  after  which  they  are  all  united  by  soldering. 

"  Fig.  372  shows  the  work  completed,  and  Fig.  373  is  from  a 
model  of  the  mouth  as  restored  with  the  crowns. 

"  In  cases  where  the  space  is  occasioned  by  the  loss  of  more 
than  one  tooth  a  somewhat  different  method  of  procedure  is 
necessary. 

"  Fig-  374  shows  a  model  of  a  mouth  in  which  the  superior 
laterals  and  centrals  had  been  extracted.  The  canines  were 
badly  decayed,  with  exposure  of  the  pulp.  The  first  step  is  the 
removal  of  the  pulps  from  the  canine  roots.     The  crowns  are 


3i8 


MECHANICAL    DENTISTRY, 


then  fitted  as  already  described  and  placed  in  position.  An 
impression  is  taken  in  plaster,  the  crowns  remaining  embedded 
on  its  removal.  The  impression  is  varnished  and  oiled,  and  a 
model  of  investing  material  poured.  After  this  has  hardened, 
the  impression  is  carefully  cut  away,  and  we  have  a  model  of 
the  mouth  with  the  crowns  in  position.  A  '  bite  '  is  taken  and 
the  articulation  secured  in  the  usual  manner.  The  remaining 
crowns,  having  been  backed,  are  fitted,  and  the  face  of  the  work 
embedded  in  investing  material. 

"  The  whole  piece  is  now  united  at  the  back  by  soldering,  and 
when  finished  presents  the  appearance  shown  at  Fig.  375. 


Fig.  374. 


Fig.  375. 


"  Fig.  376  shows  a  model  of  the  mouth  after  the  bridge  has 
been  cemented  in  place. 

"  Fig-  377  's  ^^  illustration  of  a  piece  of  this  work  for  which 
there  is  a  very  frequent  demand.  It  is  for  supplying  the  loss  of 
the  first  molar  and  bicuspids.  If  the  canine  is  intact,  the  anterior 
end  of  the  bridge  may  be  attached  by  a  strong  band  of  clasp 
metal  passing  around  the  canine,  partly  beneath  the  margin  of 
the  gum,  so  as  to  present  the  least  possible  exposure.  If,  as  is 
frequently  the  case,  there  is  extensive  decay,  it  will  be  best  to 
excise  the  remaining  portion  of  the  tooth  and  replace  an  artifi- 
cial crown  as  shown  in  the  illustration.  A  gold  cap  is  then 
made  for  the  second  molar.     If  this  tooth  is  decayed  it  will  only 


BRIDGE-DENTURES. 


319 


be  necessary  to   remove   the   decay,  and   the   cement  which   is 
used   for   setting   the   bridge  will  make  the   most  perfect  filling 

Fig.  376. 


material    beneath    the  _gold  cap.     The   intervening   molar  and 
bicuspid  crowns  are  made  in  the  following  manner:  the  porce- 

FiG.  377. 


lain  faces  are  backed  with  gold  or  platinum  and  the  tips  ground 
squarely  off.     Zinc  pattern  dies,  an  assortment  of  which  should 


120 


MECHANICAL    DENTISTRY. 


be  made  from  the  grinding  surfaces  of  molars  and  bicuspids,  are 
used  for  swaging  from  pure  gold  a  tip  or  cap  for  the  protection 
of  the  porcelain  face;  for  without  this  protection  the  porcelain 
would  be  almost  certain  to  be  broken.  The  concave  surface  of 
these  tips  is  filled  by  melting  coin-gold  into  them.     This  surface 

Fig.  378. 


is  then  ground  smooth  and  fitted  to  the  squared  surface  of  the 
porcelain  face  and  waxed  in  position.  Triangular  pieces  of  plat- 
inum are  then  cut  of  the  proper  size  to  fit  the  sides  of  the  tooth, 
waxed  in  position,  and  the  whole  invested,  leaving  the  back  open, 
which  is  filled  with  coin-crold. 


Fig.  379. 


r 


"  These  teeth  are  then  fitted  into  position  in  th^^ridge,  as 
previously  described. 

"  Fig.  379  shows  the  completed  work  in  the  mouth. 

"  Where  only  one  molar  or  bicuspid  is  lost,  sufficient  support 
may  be  gained  by  the  cap,  which  is  made  to  pass  over  the  ad- 
joining molar.     If  the  first   molar  and  second  bicuspid  are  lost. 


BRI DGE-DENTURES. 


321 


the  anterior  end  of  the  bridge  may  receive  sufficient  support 
from  a  strong  spur  (Fig.  380),  which  may  rest  in  the  groove  or 
sulcus  between  the  cusps  of  the  first  bicuspid ;  or  this  groove 
may  be  deepened  into  a  cavity,  into  which  the  spur  projects 
and  around  which  a  filling  is  placed. 

"  The  most  extensive  pieces  of  this  work  which  have  been 
attempted  are  cases  of  twelve  and  fourteen  teeth  upon  three  and 
four  roots.  Several  of  these  have  been  worn  for  a  year  or  more, 
and  none  of  which  I  have  any  knowledge  shows  any  signs  of 
failure. 

Fig.  381. 


Fig.  380. 


"Perhaps  I  cannot  better  close  this  paper  than  with  the  de- 
scription of  the  restoration  of  a  mouth  where  any  attempt  to 
remedy  the  ruin  save  by  extraction  would  have  been  considered 
madness ;  and  yet  the  lady  for  whom  this  work  was  accom- 
plished is,  to-day,  so  far  as  appearance,  utility,  and  comfort  are 
concerned,  enjoying  as  perfect  a  denture  as  any  person  who  has 
the  same  number  of  natural  teeth  intact. 

"  F'&-  381  "^^'^^  drawn  from  a  model  of  the  mouth  as  presented. 
Only  one  tooth  remained  the  pulp  of  which  was  not  exposed — 
the  left  second  superior  molar.  In  the  first  bicuspid,  canine,  and 
central  of  the  left  side  the  pulps  were  exposed  and  in  a  partially 
putrescent  condition.  Abscesses  had  formed  about  the  roots  of 
21 


322 


MECHANICAL    DENTISTRY. 


the  second  left  bicuspid,  right  central,  canine,  and  second  bicus- 
pid. The  pulp  was  slightly  exposed  and  inflamed  in  the  right 
first  superior  molar.  The  second  bicuspid  on  the  right  side  and 
both  bicuspids  on  the  left  were  extracted  at  once  as  worthless. 
The  exposed  pulp  in  the  right  molar  was  treated  and  capped. 
The  partially  living  pulps  were  removed  from  the  teeth  above 
mentioned,  the  fistulous  openings  were  healed,  and  all  of  the 
roots  thoroughly  cleansed,  and  plugged  with  orange-wood 
saturated  with  carbolic  acid  and  glycerin.  The  greatest  diffi- 
culty was  encountered  in  the  treatment  of  the  right  canine  root, 
which  had  two  large  openings  through  the  side  of  it,  and  through 

Fig.  382. 


which  projected  into  the  enlarged  pulp-canal  a  tumefied  growth 
of  the  pericementum.  For  several  weeks  the  tissues  around 
this  root  were  highly  inflamed,  and  the  face  was  several  times 
badly  swollen.  The  difficulty  was  finally  overcome  by  covering 
these  openings  with  No.  30  gold  foil  and  filling  the  root  with 
amalgam.  Crowns  were  then  fitted  over  all  of  the  roots.  A  bridge 
was  then  extended  from  the  left  canine  to  the  first  molar  to 
restore  the  lost  bicuspids.  The  missing  bicuspid  on  the  right 
side  was  restored  by  attaching  the  crown  to  the  cap  which  was 
placed  over  the  molar  containing  the  exposed  pulp. 

"  Fig.  382  was  drawn  from  a  model  of  the  mouth  as  restored. 


BRIDGE-DENTURES.  323 

"  In  conclusion,  I  desire  only  to  repeat  what  I  have  already 
substantially  said,  that  this  work  opens  up  a  new  field  for  the 
usefulness  of  our  profession,  which  will  bring  joy  to  the  heart 
of  every  conscientious  dentist.  Its  possibilities  are  almost 
unlimited." 

A  continuation  of  the  subject  of  bridge-work,  with  illus- 
trative cases,  by  Dr.  Williams,  is  contained  in  a  later  number 
of  the  Dental  Cosmos.  These  descriptions  are  introduced  here, 
accompanied  by  some  preliminary  comments  on  the  antecedent 
treatment  of  the  organs  of  support,  a  precautionary  measure 
which  all  recognize  as  of  vital  importance,  especially  in  con- 
nection with  artificial  substitutes  immovably  fixed  in  the  mouth. 
The  following  is  the  contribution  referred  to,  a  portion  of  the 
preliminary  matter  being  omitted  : — 

"  Knowing  that  the  value  of  these  artificial  substitutes  for  the 
natural  teeth  is  entirely  dependent  upon  the  conservation  of  the 
teeth  or  roots  upon  which  they  are  mounted,  and  believing  that 
the  methods  of  treating  these  roots  which  have  been  worked 
out  in  connection  with  the  system  known  as  crown-  and  bridge- 
work  are  superior  to  those  practised  by  the  majority  of  the 
profession,  I  am  di^sposed  to  devote  considerable  space  to  this 
part  of  my  subject.  Before  describing  the  several  modifications 
of  bridge-work  illustrated  in  this  article,  I  desire  to  call  atten- 
tion to  a  few  of  the  cases  which  I  have  treated,  and  which  are 
more  or  less  radical  departures  from  those  ordinarily  met  with. 

"  Case  I. — This  case  was  reported  in  the  Independent  Practi- 
tioner, and  from  it  I  quote  as  follows :  '  Mrs.  S.  had  been 
wearing  a  pivot-tooth  on  the  root  of  the  upper  right  central  for 
several  years,  and  as  it  required  frequent  re-setting  she  desired 
to  have  it  replaced  by  a  more  permanent  operation.  On  remov- 
ing the  crown  the  root  was  found  in  a  bad  condition.  Decay 
had  penetrated  the  side  of  the  root,  leaving  quite  a  large  opening 
into  the  pericementum.  An  enlarged  foraminal  opening  led  to 
a  cavity  at  the  end  of  the  root,  from  which  an  offensive  pus  was 
discharged.  But  the  root  was  very  firm,  and  promised  to  give 
a  secure  foundation  for  a  crown  if  it  could  be  brought  into  a 
healthy  condition.  A  little  cowardice  prompted  me  to  attempt 
the  treatment  through  the   root,  but  after   a  week's  effort  my 


324  MECHANICAL    DENTISTRY. 

ambition  in  that  direction  was  satisfied,  and  I  resorted  to  a 
method  which  has  proved  eminently  successful  in  several  cases 
of  this  character.  The  end  of  a  soft,  smooth  broach  was  bent 
so  as  to  form  a  little  hook.  This  was  passed  up  the  enlarged 
pulp-canal  until  the  hook  slipped  over  the  end  of  the  root.  The 
broach  was  then  seized  with  pliers  at  a  point  exactly  opposite 
the  external  end  of  the  root  and  drawn  out  and  the  length 
carefully  measured. 

"  '  A  point  of  orange-wood  was  carefully  shaped  to  fit  the 
pulp-canal,  a  notch  cut  on  one  side,  showing  the  exact  length  of 
the  root  inside,  and  after  dipping  in  a  solution  composed  of  equal 
parts  of  carbolic  acid,  chloral  hydrate,  and  gum  camphor,  it  was 
driven  into  the  canal  until  the  notch  appeared  precisely  opposite 
the  end  of  the  root.  I  know  of  no  other  method  by  which  an 
enlarged  pulp-canal  can  be  so  perfectly  filled,  with  a  certainty 
that  the  filling  material  has  gone  exactly  to  the  end  of  the  root, 
and  no  further. 

" '  The  wood  point  was  twisted  off  at  a  point  about  half  the 
length  of  the  root,  where  it  had  been  weakened  by  passing  a 
knife  around  it,  cutting  partly  through.  Heavy  gold  foil  was 
placed  over  the  opening  in  the  side  of  the  root,  and  the  large 
funnel-shaped  opening  filled  with  amalgam.  An  external  open- 
ing was  made  opposite  the  end  of  the  root,  and  the  diseased 
bone  and  end  of  the  root  cut  away  with  rose-burs.  A  cotton 
tent  was  kept  in  for  two  days.  On  the  third  day  a  crown  was 
placed  on  the  root,  and  in  ten  days  the  external  opening  healed 
and  all  irritation  had  passed  away.' 

"Case  II. — Mr.  W.  had  a  central  incisor  broken  near  the 
margin  of  the  gum  by  a  base-ball.  The  pulp  was  removed  and 
the  canal  filled  with  gutta-percha.  Inflammation  followed  and 
an  abscess  threatened,  which  was  prevented  by  removing  the 
filling.  When  he  came  to  me  the  canal  had  been  open  for  more 
than  a  year,  and  from  it  there  had  been  more  or  less  constant 
discharge.  On  examination  I  found  it  filled  with  black  and  very 
offensive  matter,  which  had  stained  the  dentine  to  a  considerable 
depth.  After  syringing  with  warm  water,  I  enlarged  the  canal 
materially  and  passed  directly  through  the  end  of  the  root  with 
a  rose-bur.     I  enlarged  the  cavity  which  I  found  at  the  end   of 


BRIDGE-DENTURES.  325 

the  root  until  I  had  produced  quite  a  copious  flow  of  blood 
through  the  canal.  After  the  bleeding  had  ceased,  a  broach 
wound  with  cotton  was  dipped  in  chlorid  of  zinc,  twenty  per 
cent,  solution,  and  passed  up  through  the  root.  After  this  treat- 
ment the  canal  was  simply  dressed  with  Listerin  for  ten  days, 
the  dressing  being  changed  every  day.  At  the  end  of  that  time, 
there  being  no  discharge  (in  fact,  I  could  not  discover  at  any 
time  after  the  operation  that  there  was  any  discharge  of  pus), 
the  root  was  filled  precisely  as  described  in  the  preceding  case, 
and  a  Richmond  crown  mounted  upon  it. 

"  I  believe  the  most  rational  treatment  for  the  persistent  patho- 
logical condition  which  remains  around  the  roots  of  teeth  which 
have  been  the  seat  of  alveolar  abscess  may  be  summarized  in  a 
single  short  sentence.  If  the  source  of  the  primary  irritation 
remains,  remove  it;  cleanse  the  root  thoroughly  and  fill  it;  then 
reduce  the  territory  of  perverted  physiological  action  to  the  condition 
of  a  simple  wound,  and  treat  it  as  such.  If  the  case  is  one  of  long 
standing,  I  enlarge  the  external  opening  and  enter  the  cavity  at 
the  end  of  the  root  with  a  large  rose-bur,  cutting  out  the  walls  of 
the  cavity  and  trimming  the  end  of  the  root.  Syringe  out  with 
warm  water ;  inject  a  ten  per  cent,  solution  of  chlorid  of  zinc, 
and  insert  a  cotton  tent  for  a  few  days.  Dress  the  wound — for 
this  is  what  you  now  have — daily,  syringing  with  peroxid  of 
hydrogen,  followed  by  Listerin.  I  believe  this  simple  treatment 
will  cure  the  most  persistent  cases  of  abscess,  or,  more  properly 
speaking,  alveolar  ulcers,  in  from  ten  days  to  two  weeks.  The 
medication  of  these  ulcerated  tracts  for  many  weeks,  and  some- 
times months,  is  neither  humane  nor  scientific  treatment. 

"  While  I  have  thus  written  encouragingly  of  the  practice  of 
retaining  pulpless  teeth  in  the  jaws,  I  would  always  <^/j"courage 
the  removal  of  healthy  pulps,  except  when  absolutely  necessary. 
But  the  operator  should  not  hesitate  to  do  this  when  convinced 
that  the  patient  will  be  greatly  benefited  by  the  insertion  of  a 
piece  of  work  which  necessitates  the  removal  of  a  healthy  pulp. 
However,  the  constant  modifications  and  improvements  in  the 
methods  of  constructing  the  work  are  making  the  removal  of 
pulps  more  and  more  unnecessary. 

"  We  will  now  proceed  to  consider  the  principal  object  of  this 


326 


MECHANICAL    DENTISTRY. 


paper,  which  is  the  illustration  and  description  of  some  of  these 
improvements. 

"  Fig.  383  shows  a  piece  of  work  made  for  a  case  of  quite  fre- 
quent occurrence.     It  represents  the   restoration  of  the   inferior 

Fig.  383. 


Fig.  384. 


bicuspids  and  first  molar  of  the  right  side.  A  gold  crown  is 
made  for  the  second  molar,  and  then  the  three  intervening  teeth 
or  '  dummies  '  are  made  as  described   in  my  former  paper.     For 

the  support  of  the  anterior 
end  of  the  bridge  the  me- 
thod hitherto  practised  has 
been  to  excise  the  crown  of 
the  cuspid  and  fit  a  porce- 
lain crown  with  gold  back- 
ing to  the  root,  and  to  this 
the  anterior  end  of  the 
bridge  is  soldered. 

"  Fig.  384  illustrates  a 
device  which  obviates  the  necessity  for  removing  the  cuspid 
crown.  A  gold  band  is  fitted  around  the  cuspid.  At  the  front, 
shown  at  a,  this  band  is  allowed  to  pass  a  little  beneath  the 
margin  of  the  gum  so  as  to  make  the  smallest  possible  exhi- 
bition of  gold.  On  the  lingual  aspect  of  the  tooth  this  band  is 
allowed  to  be  nearly  the  length  of  the  crown.  It  will  be  seen 
that  when  this  band  is  fitted  as  perfectly  as  possible  there  must 
necessarily  be  quite  a  vacancy  between  the  upper  part  of  the 
lingual  surface  of  the  tooth  and  the  band.  It  is  important  that 
this  portion  of  the  band  fit  the  tooth  perfectly,  and  an  accu- 
rate adaptation  is  obtained  as  follows  :  A  piece  of  pure  gold, 
rolled  to  No.  35  American  gauge,  is  fitted  over  that  portion  of 
the  lingual  surface  of  the  tooth  which  it  is  desired  to  cover,  d, 
in  Fig.  384,  shows  the  shape  that  this  little  pure-gold  plate 
usually  assumes.     It  can  easily  be  fitted  perfectly  by  the  use  of 


BRIDGE-DENTURES. 


a  burnisher,  and  then,  with  the  band  in  position,  a  drop  of  melted 
resin  wax  is  flowed  into  the  space  between  the  pure  gold  and  the 
band.  It  is  now  removed  from  the  tooth,  invested,  and,  after 
melting  out  the  wax,  solder  is  flowed  into  the  vacancy,  filling 
completely  the  space  occupied  by  the  wax.  The  top  of  the 
lingual  portion  will  now  be  thicker  than  is  necessary,  but  can  be 
easily  ground  or  filed  down  to  the  proper  thickness.  We  now 
have  a  band  which  fits  all  portions  of  the  tooth  perfectly.  The 
anterior  end  of  the  bridge 
is  soldered  to  this  band,  and 
after  the  work  is  properly 
finished  it  is  cemented  in 
place  in  the  usual  man- 
ner, b  and  c,  show  side 
and  lingual  views  of  this 
band  after  the  fitting  is 
completed. 

"Figs.  385,  386, and  387 
illustrate  a  method  of  'in- 
serting extensive  pieces  of 

bridge- work  incases  where  there  are  no  natural  teeth  or  roots  for 
supporting  one  end  of  the  bridge.     The  work  from  which  these 


Fig.  386. 


Fig.  387. 


drawings  were  made  was  constructed  by  Dr.  H.  A.  Parr,  of  New 
York.     By  this  method  bridges  may  be  inserted  in  cases  where 


328  MECHANICAL    DENTISTRY. 

all  of  the  teeth  on  one  side  of  the  mouth  have  been  lost,  or  where 
all  of  the  teeth  anterior  to  the  molars  on  both  sides  are  wanting. 
Crowns  are  first  fitted  to  the  teeth  which  remain.  These  crowns 
being  in  position,  an  impression  is  taken.  From  this  a  cast  is 
obtained  with  the  crowns  in  their  proper  positions.  A  second 
impression  is  also  taken  of  that  portion  of  the  mouth  where  there 
is  no  natural  support  for  the  bridge.  From  this  impression 
metallic  dies  and  counter-dies  are  obtained,  from  which  is 
'  struck  '  a  small  gold  plate  about  three-fourths  of  an  inch  in 
length  and  width,  the  size  of  the  plate  varying  according  to  posi- 
tion and  other  conditions.  After  this  little  plate  or  '  saddle  '  has 
been  perfectly  fitted,  it  is  waxed  in  the  proper  position  on  the 
model  with  the  crowns.     The  intervening  teeth  are  now  placed 


in  position,  and  the  work  invested  and  soldered.  I  have  had  no 
practical  experience  with  this  method,  but  Dr.  Parr  informs  me 
that  he  has  inserted  several  cases  which  are  being  worn  with 
perfect  satisfaction.  To  provide  for  the  possibility  of  shrinkage 
or  absorption  at  the  point  where  the  plate  or  saddle  rests,  I 
would  suggest  that  it  be  not  soldered  to  the  bridge,  but  attached 
by  means  of  an  adjustable  screw.  * 

"  Fig.  388  illustrates  another  device  for  obviating  the  necessity 
for  removing  the  crowns  of  natural  teeth  in  preparing  the  mouth 
for  bridge-work.  Crowns  are  fitted  in  the  mouth  to  the  points 
of  attachment  in  the   usual  manner.     An  impression  is  taken, 

*  Too  extensive  use  of  this  method  of  bridging,  with  plate  or  "  saddle,"  should 
not  be  made,  on  account  of  the  inability  of  the  patient  to  keep  it  clean. — Ed. 


BRIDGE-DENTURES. 


329 


bringing  the  crowns  away  in  their  proper  positions.  From  this 
the  cast  or  model  is  obtained.  Heavy  bands  of  half-round  gold 
or  platinum  bars  are  now  fitted  around  the  necks  of  the  natural 
teeth  on  their  lingual  surfaces.  These  bands  being  waxed  in 
position,  serve  to  connect  the  different  parts  of  the  bridge,  unit- 
ing them  in  one  piece  without  the  loss  of  any  of  the  natural 
crowns.  I  have  found  this  a  highly  satisfactory  method  of  in- 
serting extensive  pieces  of  the  work.  Fig.  389  shows  the  mouth 
as  presented  for  which  the  piece  shown  was  constructed.  Fig. 
390  shows  the  piece  in  position. 

"  Fig.  391  illustrates  a  case  which  is  a  type  of  a  class  of  frequent 

Fig.  389. 


occurrence.  Alternate  molars  and  bicuspids  in  the  upper  and 
lower  jaws  are  lost,  until  the  occlusion  is  somewhat  changed, 
and  the  force  of  mastication  is  gradually  brought  upon  the  front 
teeth.  Rapid  wearing  of  these  teeth  results.  The  cases  are 
among  the  most  difficult  that  the  operator  is  called  upon  to  treat 
by  the  ordinary  methods.  In  the  case  herewith  illustrated,  the 
lower  bicuspids  with  a  molar  on  one  side  were  in  good  condi- 
tion, but  the  loss  of  the  upper  bicuspids  and  molars  made  them 
useless.  As  usually  happens,  the  upper  incisors  had  suffered  most. 
The  lower  incisors  were  restored  by  capping  them  with  cohesive 
foil.     The  bridge   shown   in    Fig.  392  was  constructed  for  the 


330 


MECHANICAL    DENTISTRY. 


Fig.  390. 


right  side  of  the  upper  jaw,  while  the  teeth  on  the  left  side  were 
restored  by  contour  work,  as  shown  in  Fig.  393. 

"  The  superiority  of  the  condition  of  this  patient's  mouth, 
which  resulted  from  this  work,  over  anything  which  could  have 
been  accomplished  by  plate  work,  is  almost  inconceivable  to  one 
not  familiar  with  these  methods. 

"The  only  annoyance  which  bridge-work  is  likely  to  cause 
patient  or  operator  is  the  occasional  breaking  of  a  porcelain,  an 
accident  of  not  frequent  occurrence.  While  the  replacing  of  a 
broken  porcelain  has  never  been  a  matter  of  extreme  difficulty, 
yet  I  have  always  regarded  the  methods  hitherto  employed  as 
more  or  less  imperfect  and  uncertain  in  their  results.  This  led 
me  to  devise  a  method  of  replacing  broken  porcelains  which 
leaves  the  work  fully  as  strong  as  before ;  a  method  which  makes 
the  operation  a  very  simple  one,  requiring  less  than  an  hour  for 

its  performance  ;  and  after 
the  porcelain  has  been  re- 
placed an  expert  would 
not  discover  any  traces  of 
an  accident.  After  re- 
moving all  traces  of  the 
broken  porcelain,  the  pro- 
jecting pins  are  cut  off, 
and  two  holes  drilled 
through  the  backing  in 
the  exact  position  occu- 
pied by  the  pins.  The  narrow  space  of  metal  now  intervening 
between  these  two  holes  is  cut  out  with  a  fissure-bur.  This 
leaves  a  groove  which  should  not  be  wider  than  the  diameter  of 
the  pins.  The  length  of  this  groove  should  now  be  increased 
on  the  lingual  surface,  but  not  on  the  front.  The  object  of  this 
is  to  give  a  dove-tail  shape  to  the  groove,  which  is  easily  effected 
by  the  use  of  the  same  fissure-bur  above  referred  to.  The  lin- 
gual appearance  of  this  groove  when  properly  shaped  is  shown 
in  Fig.  394.  The  proper  tooth  is  selected,  the  pins  passed 
through  this  hole  and  bent  outward  into  the  dove-tail  groove. 
It  will  be  found  almost  impossible  to  bend  these  pins  into  their 
proper  positions  by  any  ordinary  means,  so  as  to  hold  the  tooth 


BRIDGE-DENTURES. 


331 


quite  rigid  and  immovable.  An  instrument  herewith  illustrated 
(Fig.  395)  accomplishes  this  feature  of  the  work  in  a  very  simple 
and  effective  manner.  Its  use  is  almost  too  nearly  evident  to 
require  description.     Both  the  rubber  pad  which  rests  upon  the 


Fig.  391. 


Fig 


porcelain  front  and  the  wedge-shaped  point  which  passes  between 
the  pins  are  made  to  rotate  in  their  sockets,  so  that  any  desired 
position  can  be  obtained.  A  firm  closure  of  the  instrument 
when  in  position  forces  the  pins  outward  into  the  dove-tail  groove, 
and  the  tooth  is  immovably  fixed  in  place.     It  now  remains  but 


Fig.  393. 


Fig.  394. 


to  fill  the  space  between  the  pins  with  any  form  of  cohesive  gold 
(I  use  crystal  gold),  and  with  corundum,  Arkansas,  and  rubber 
points  in  the  engine  the  surface  is  finished  and  polished.  The 
wedge-shaped  filling  of  crystal  gold  acts  as  a  keystone  between 
the  pins,  and  makes  a  most  perfect  method  of  repair. 


332 


MECHANICAL    DENTISTRY. 


"  The  practice  of  extracting  badly-decayed  and  broken-down 
teeth,  particularly  when  they  become  a  source  of  constant  annoy- 
ance, and  replacing  them  with  artificial  substitutes  mounted 
upon  rubber,  celluloid,  or  metallic  plates,  has  become  so  firmly 
established  in  the  public  and  professional  mind  as  the  proper 
and  unavoidable  thing,  that  the  folly  of  such  practice  can  only 
be  demonstrated  by  persistent  and  long-continued  endeavor. 
The  statement,  therefore,  that  it  is  no  less  a  criminal  practice,  in 
principle  if  not  in  degree,  to  extract  a  tooth  because  it  is  in  an 
ulcerated  or  broken-down  condition,  than  would  be  that  of  ampu- 
tating a  finger  because  of  the  appearance  of  a  felon,  or  removing 
an  eye  to  get  rid  of  a  cataract,  will  seem  a  radical  one.  But  if 
my  experience  has  taught  me  anything,  it  certainly  is  no  exag- 

V\c.  395. 


geration  of  fact.  Diseases  of  the  teeth  and  the  surrounding 
tissues  are  certainly  as  amenable  to  treatment  as  are  ulcers  or 
morbid  growths  in  other  parts  of  the  body.  The  only  conditions 
necessary  to  the  successful  accomplishment  of  this  are  requisite 
knowledge  and  skill  in  the  operator  and  a  desire  on  the  part  of 
the  patient  to  have  a  healthy  mouth. 

"  A  properly  made  artificial  crown  mounted  upon  a  root,  the 
investing  membrane  of  which  is  in  a  healthy  condition,  is  quite 
as  useful,  and,  all  points  considered,  perhaps  quite  as  desirable, 
as  a  pulpless  tooth  with  its  natural  crown  intact.  Such  is  my 
confidence  in  the  intrinsic  merit  of  bridge-work  that  I  think  it 
requires  no  very  great  degree  of  foresight  to  predict  that  the 
day  is  not  far  distant  when  a  large  per  cent,  of  the  now  prevalent 
partial-plate  work  will  be  a  thing  of  the  past." 


BRI DGE-DENTURES. 


JJO 


Dr.  Knapp's  Method. — After  constructing  the  crowns  as 
directed  on  page  241,  suitable  plain  plate-teeth  should  be  backed 
with  pure  gold  and  built  up  to  the  desired  shape  with  wax,  Fig. 
396,  which  should  be  incased  in  pure  gold  as  before  described, 
Figs.  397,  398,  399.  After  investing  arid  subsequent  removal  of 
the  wax,  the  resulting  receptacle  can  readily  be  filled  with  twen- 
ty-carat solder,  Fig.  400. 

In  the  preparation  and  in  the  drilling  of  the  roots,  great  care 
should  be  exercised  to  have  the  caps  and  the  pins  as  nearly  par- 
allel as  possible.  Here,  as  well  as  elsewhere,  sound  judgment 
is  essential  to  the  accomplishment  of  the  best  results.  For  the 
attainment  of  accuracy,  it  is  essential  that  an  impression  should 
be  taken,  preferably  in  plaster,  of  the  caps  in  their  proper  posi- 
tions upon  their  several  roots.     An  impression  should  likewise 


Fig.  396. 


Fig.  397.        Fig.  399.  Fig.  401. 


Fig.  402. 


be  taken  of  the  occluding  teeth.  The  models  obtained  from 
these  impressions  should  then  be  placed  in  an  articulator,  as  for 
plate  work,  and  the  articulating  surfaces  of  the  porcelain  crowns 
should  be  carved  in  wax  to  a  nicety.  By  the  methods  just 
mentioned  these  occluding  surfaces  are  reproduced  in  gold.  The 
requisite  exercise  of  the  dental  organs  and  immunity  from  break- 
age of  porcelain  faces  are  in  this  way  secured.  The  porcelains 
should  not  press  upon  the  gums  except  in  the  anterior  portion 
of  the  mouth,  where  the  formation  of  the  alveolar  process  per- 
mits and  the  perfection  of  speech  demands  it.  The  gold  from 
the  grinding  surfaces  should  form  a  gradual  slope  until  it  reaches 
the  porcelain,  and  should  be  entirely  free  from  pits  and  other 
irregularities.  When  they  occur,  it  becomes  necessary  to  remedy 
these  as  well  as  other  defects.     This  is  to  be  done  by  the  re-firing 


334  MECHANICAL    DENTISTRY, 

of  either  a  single  crown  or  an  entire  piece  of  bridge-work.  At 
times  gold,  where  needed,  may  be  added  by  the  use  of  the  elec- 
tric mallet,  and  a  beautiful  finish  obtained  with  it.  Under  all 
circumstances,  both  porcelain  and  gold  should  present  a  perfect 
continuity  of  surface.  With  diligent  attention  given  to  the  im- 
portant details  of  construction  which  are  here  pointed  out,  the 
great  bugbear  of  uncleanliness,  suggested  as  an  objection  to 
this  method  of  substitution,  is  entirely  removed.  Of  course, 
food  and  salivary  deposits  will  accumulate  around  artificial 
crowns  as  well  as  about  natural  teeth,  and  the  personal  cleanli- 
ness of  the  wearer  is  the  greatest  and  indeed  sole  safeguard 
against  such  injurious  accretions  with  any  denture.  A  philoso- 
phy that  would  condemn  the  insertion  of  bridge-work,  artisti- 
cally constructed  on  scientific  principles,  on  the  score  of  unclean- 
liness, would  as  consistently  advise  the  extraction  of  the  natural 
organs  for  the  reason  that  their  possessor  was  a  sloven.  "  Clean- 
liness is  next  to  godliness,"  says  Wesley,  and  he  who  expects  to 
wear  a  "  crown,"  here  or  hereafter,  must  heed  this  maxim. 

Fig.  401  shows  an  upper  central  and  lateral  incisor  mounted 
upon  a  central  root  with  spud  attachment.  Fig.  402  represents 
the  four  upper  front  teeth  held  in  position  by  the  two  lateral 
roots.  Fig.  403  the  six  upper  front  teeth  mounted  upon  the  two 
cuspid  roots.  Fig.  404  represents  a  full  upper  denture  with  the 
two  cuspid  roots  and  two  molars  as  anchorages. 

For  the  attachment  of  crown  and  bridge-work  the  best  attain- 
able oxyphosphate  cement  should  be  used.  With  the  pins 
notched,  and  the  roots  perfectly  free  from  moisture,  sufficient 
oxyphosphate  should  be  placed  around  each  pin  and  inside  of 
the  collar  to  completely  fill  all  the  space  between  the  pin  and 
the  canal,  the  collar  and  the  root.  Firm,  well-directed  pressure 
should  then  be  exerted  to  carry  the  piece  to  its  proper  position, 
where  it  should  be  held  for  a  few  minutes  to  permit  of  the 
hardening  of  the  cement,  all  excess  of  which  oozing  through  at 
the  edge  of  the  collar  should  be  carefully  removed.  Before 
being  dismissed  the  patient  should  be  instructed  to  be  a  little 
cautious  in  regard  to  subjecting  the  crown  or  bridge  to  any 
force  for  a  short  time. 

Dr.  Low's  Method. — The  following  illustrated  account  de- 


BRIDGE-DENTURES. 


335 


scriptive  of  Dr.  J.  E.  Low's  methods  of  procedure  in  the  cases 
under  consideration  was  especially  prepared  by  him  for  this 
work.  His  definition  of*  bridge-work  "  has  special  application 
to  his  distinctive  method  of  construction.     It  is  as  follows  : — 

"  Bridge-work  consists  of  supplying  vacancies  between  teeth 
or  roots  with  artificial  teeth,  attached  to  the  adjoining  natural 
teeth  or  roots  by  means  of  bands  or  crowns,  and  held  in  such  a 
position  that  there  is  no  contact  with  or  pressure  on  the  gums 
beneath,  and  thus  no  opportunity  for  secretions  or  other  foreign 
matter  to  be  held  there,  and  thereby  become  offensive. 

"  There  is  really  but  one  kind  of  bridge-work,  and  but  one  way 
to  make  bridge-work  to  insure  success.     There  are  many  ways 

Fig.  404. 


of  making  teeth  without  plate,  but  this  is  not  bridge-work.  I 
will  here  try  to  explain  in  detail  my  manner  of  making  and 
adjusting  bridge- work. 

"  For  the  first  illustration,  as  seen  in  Fig.  405,  we  have  a  case 
where  all  the  teeth  have  been  extracted  except  the  two  cuspids 
and  two  second  molar  roots. 

"  We  first  proceed  to  prepare  the  roots  by  crowning.  I  use 
gold  crowns  on  the  molar  teeth,  and  what  is  known  as  the  Low 
crown  on  the  cuspids.  The  preparation  of  the  two  cuspids  con- 
sists in  making  the  crown  ready  for  adjustment,  the  process  of 
which  is  described  in  detail  in  another  part  of  this  work  (page 
258).     I  always   measure   the   tooth   to  be  crowned  with  gold 


336 


MECHANICAL    DENTISTRY, 


with  a  strip  of  block  tin,  No.  35  thick  Stub  gauge  or  there- 
abouts. Place  the  tin  around  the  tooth  and  with  pliers  care- 
fully measure  the  full  size  of  the  same. 

"  Should  you  be  measuring  a  tooth,  or  part  of  a  tooth,  on  which 
there  are  projections,  take  the  engine,  and  with  a  stone  grind  off 
the  same,  making  a  smooth  surface,  so  there  will  be  nothing  to 
interfere  with  the  fitting  of  the  bands  properly.  After  cutting 
the  tin  measures  by  the  marks  made  by  the  pliers,  you  have  the 
measures  ready  to  make  the  gold  bands  by.  Cut  the  bands  and 
bevel  the  edges  and  solder  together,  and  you  are  ready  to  fit. 
After  fitting  all  the  bands  and  finishing  the  crowns  in  the  usual 

Fig.  405. 


way,  I  place  each  in  position  in  the  mouth,  having  previously  re- 
gulated the  articulation  of  each  crown  as  desired,  in  the  process 
of  making.  We  now  take  a  deep  articulation  in  wax,  and  im- 
pression in  plaster-of-Paris  ;  remove  before  it  gets  too  hard,  and 
place  all  the  crowns  in  their  positions  in  the  impression  ;  varnish, 
oil,  and  pour  in  the  usual  way  ;  separate  the  cast  from  the  impres- 
sion and  place  in  the  articulator.  Then  pour  with  plaster.  After 
the  plaster  has  hardened,  remove  the  wax,  and  we  have  the  articu  - 
lation  proper,  and  are  ready  to  select  and  grind  our  teeth,  having 
previously  selected  our  shade.  My  experience  has  long  ago 
taught  me  that  no  porcelain  tooth  can  stand  the  pressure  for 
bridge-work,  the  strain  on  them  being  twice  as  great  as  with  teeth 


BRIDGE-DENTURES.  337 

on  plates  which  rest  on  the  gums,  that  give  to  pressure.  In  order 
to  prevent  breakage  of  teeth  and  give  strength,  I  have  for  many 
years  been  making  a  tooth  with  gold  cusps.  I  will  here  describe 
my  manner  of  doing  so. 

"  For  the  first  step,  I  use  No.  28  gauge  platinum  for  a  cover- 
ing of  the  inside  of  the  tooth,  or  just  where  you  wish  gold  to  flow. 
Then  I  bend  the  pins  down  to  hold  the  platinum  in  position,  and 
with  a  file  remove  all  overlapping  platinum  to  prevent  breaking 
of  our  tooth  in  heating.  The  tooth  is  made  flat  on  the  crown 
surface  with  the  express  intention  of  restoring  with  a  gold  crown. 
This  crown  need  not  be  very  thick,  but  should  perfectly  resemble 
the  cusps  on  the  natural  tooth,  for  the  purpose  of  mastication. 
As  these  cusps  are  not  on  the  market,  and  every  dentist  making 
bridge-work  cannot  make  it  in  a  way  to  stand  without  putting 
gold  cusps  on  the  grinding  surface  of  the  bicuspids  and  molars, 
I  will  here  describe,  for  the  benefit  of  those  who  do  not  know  how 
to  make  them,  how  they  can  be  made  with  very  little  trouble. 
Pick  out  a  natural  tooth  with  cusps  the  exact  shape  you  wish  to 
have  your  gold  cusps  resemble ;  mix  up  some  fire  clay  in  a  thick 
paste  ;  then  press  your  tooth  into  it  a  little  deeper  than  you  wish 
the  cusps.  Having  made  the  proper  impression,  remove  the 
tooth,  and  set  the  impression  over  the  gas  stove  to  dry.  After 
it  is  dried  and  reasonably  hot,  lay  your  pieces  of  gold  in  the  im- 
pression and  with  a  blowpipe  melt  them.  When  melted,  press 
with  a  piece  of  steel  on  the  gold  till  cool.  This  mold  will  do  to 
make  many  from.  If  you  have  not  the  fire  clay,  and  can  get 
charcoal  that  is  burned  from  fine-grained  wood  and  is  soft,  you 
can  simply  press  your  tooth  into  the  charcoal  and  melt  in  the 
same  way,  or  you  can  carve  your  teeth  as  you  desire  in  a  block 
of  carbon.  Of  course,  the  little  steel  dies  are  handier,  as  we  can 
swedge  up  our  gold  cusps  in  them,  either  solid  or  thin. 

"  Having  described  our  manner  of  making  the  cusps,  we  will 
now  return  to  the  manner  of  finishing  our  tooth.  We  left  ofl"by 
saying  we  covered  the  inside  and  bent  down  the  pins  and  filed  off 
the  overlapping  platinum.  We  now  place  our  cusp  on  the  top 
of  the  tooth,  and  place  in  the  position  desired,  holding  it  there 
with  wax,  and  with  a  spatula  trim  the  wax  the  exact  shape  we 
wish  our  tooth  to  be,  V-shaped,  tapering  from  the  crown  down. 
22 


338 


MECHANICAL    DENTISTRY. 


We  now  encase  in  plaster  and  sand,  which  gives  us  a  box.  When 
hard,  remove  the  wax  and  place  over  the  stove,  and  when  suf- 
ficiently dry,  fill  in  with  coin-gold,  using  the  blowpipe  to  melt 
it  in  a  solid  mass,  and  our  tooth  is  ready  to  file  up  and  place  in 
position  on  the  articulator.  Fig.  406  shows  the  tooth  in  this 
condition. 

"  After  our  teeth  are  arranged,  we  hold  the  same  in  position 
with  wax,  remove  from  the  articulator,  encase  with  plaster  and 
sand  or  asbestos  in  the  usual  way.  That  we  may 
have  a  strong  case,  I  always  use  platinum  wire  be- 
tween each  tooth,  and  then  proceed  to  heat  and 
solder.  Be  sure  that  all  the  gold  cusps  are  so  arranged 
that  you  can  get  it  all  soldered  together,  as  this  gives 
us  great  strength.  My  formula  for  solder,  which  I  have  used  for 
many  years,  and  which  will  be  found  very  easy-flowing,  and 
almost  the  exact  color  of  the  gold  you  are  using,  is  as  follows  : 


Fig,  406. 


Fig.  407. 


Always  figure  from  the  carat  of  gold  you  are  working.  Take  i 
dwt.  coin-gold,  2  grains  of  copper,  and  4  of  silver.  We  now  have 
our  case  soldered  ;  after  filling  as  desired,  commence  to  finish 
with  felt  wheels  and  pumice  stone,  after  which  use  rouge  buff 
wheels.  It  is  now  ready  for  adjustment  in  the  mouth.  In  Fig. 
407  we  see  the  case  ready  for  adjustment. 

"  Have  the  assistant  dry  all  the  teeth  or  roots  to  be  operated 
upon  while  you  are  mixing  the  cement.  Be  sure  and  use  a  kind 
which  will  not  harden  very  rapidly,  or  your  cement  will  set  be- 
fore you  get  your  teeth  adjusted.  Use  sufficient  cement  to  fill 
all  the  gold  crowns  perfectly  when  the  case  is  driven  to  place. 
Moisten  the  step-plugs  and  cap  with  cement,  touching  every  por- 
tion, and  with  an  instrument  place  a  little  cement  in  the  bottom 


BRIDGE-DENTURES. 


339 


of  the  cavity.  We  now  adjust  our  case,  using  the  little  roter 
for  the  Low  crowns  and  a  piece  of  ivory  for  driving  on  the 
gold  crowns.     Fig.  408  represents  the  case  when  in  position. 

"  It  will  be  seen  by  looking  at  the  previous  cut  (Fig.  407),  that 
the  teeth,  after  having  been   soldered,  are  all  spaced  fully  one- 

FiG.  408. 


third  of  the  distance  from  the  place  01  contact  with  the  gums 
and  the  grinding  surface  of  the  teeth,  so  that  secretions  could 
not  possibly  lodge  there.  I  have  given  a  description  of  my 
manner  of  making  a  full  upper  case  of  bridge-work  where  there 
are  roots  to  be  crowned  to  support  the  bridge.  I  will  now 
describe  my  manner  of  op- 
erating upon  a  case  where  —  ^09- 
the  four  centrals  are  miss- 
ing, as  seen  in  Fig.  409  ; 
to  supply  these  four  teeth 
where  the  cuspids  are  in- 
tact, I  use  a  gold  band. 

"  I  first  measure  the  tooth 
with  strips  of  tin,  and  make 
the  gold  bands,  as  before 
described  ;  cut  out  the  out- 
side lower  portion  of  the 
band  before  beginning  to  fit.  In  fitting,  as  the  band  is  being 
driven  down,  cut  away  any  of  the  band  that  touches  the  gum 
before  all  touches  ;  never  drive  the  band  any  distance  under  the 
gum,  as  inflammation  would  probably  follow. 

"  I  mention  this,  as  I  have  seen  many  attempts  to  get  rid   ot 


340 


MECHANICAL    DENTISTRY. 


the  band  by  driving  up  under  the  gums  and  cutting  them  out  on 
the  front,  until  they  were  too  narrow  for  strength.  It  is  hard 
work  to  make  something  out  of  nothing.  The  bands  should 
be  heavy  and  strong,  and  the  patient  made  to  understand  that  if 
he  expects  to  get  rid  of  the  annoyance  of  the  plate,  he  must 
sacrifice  his  dislike  to  showing  gold.  After  driving  the  bands 
up  to  the  margin  of  the  gums,  as  the  cuspid  teeth  are  very 
tapering,  the  bands  will  have  to  be  taken  in  at  the  bottom.  To 
do  this  slit  the  band  about  a  third  of  its  length  up,  then  place 
it  on  the  tooth  again,  lap  it  over  enough  to  bring  it  to  a  close  fit 
and  then  take  it  off  and  solder. 

"  Continue  taking  it  in  wherever  it  does  not  perfectly  fit  the 
tooth,  and  after  a  good  fit  is  obtained  proceed  as  before  described, 
by  taking  an  articulation  and  impression.  In  adjusting,  first  try 
the  case  on  to  see  that  it  fits,  and  that  the  articulation  is  all  right. 
Next  have  the  assistant  dry  the  teeth  upon  which  the  bands  are 
going,  and  then  mix  your  cement.  This  should  be  mixed  to 
about  the  consistency  of  thick  cream.  It  must  be  neither  too 
thick  nor  too  thin,  or  the  adhesion  will  not  be  strong  enough  to 
hold.  Cover  your  teeth  with  cement  and  then  the  inside  of  the 
bands.  Place  these  on  the  teeth  and  carefully  mallet  to  position. 
For  this  purpose  I  use  a  steel  instrument,  with  a  crease  or  groove 
in  the  end.     The  teeth   must  be  kept  dry,  after  the  case  is  in 

position,  until  the  cement 
is  well  set.  After  this  is 
done,  bevel  the  edges  of 
the  bands  and  burnish 
close  to  the  teeth,  and  if 
burnished  properly  they 
will  be  made  to  resemble 
gold  fillings.  Fig.  410 
represents  the  case  com- 
pleted. 

"  I  am  aware  that,  in  a 
case  like  this,  porcelain 
crowns  instead  of  gold 
bands  could  be  used,  and  I  should  consider  it  much  preferable 
to  do   so  where  we    have    roots   or   unsound    teeth  to  operate 


Fig.  410. 


BRIDGE-DENTURES.  34 1 

upon,  but  do  not  advise  the  destroying  of  nerves,  where  the 
teeth  are  intact,  to  supply  such  a  case  with  crowns,  as  the  bands 
will  answer  every  purpose  for  many  years. 

"  If  they  should  give  out  in  after  years,  the  roots  can  then 
be  crowned.  I  have  many  of  these  cases  that  have  been  in 
use  eight  and  nine  years,  some  of  which  have  never  loosened, 
and  some  I  have  reset  nearly  every  year.  I  always  impress 
upon  the  patient  the  necessity  of  having  them  reset  imme- 
diately should  they  become  loose,  and  advise  them  to  have  their 
cases  examined  at  least  once  a  year.  Should  parties  insist 
upon  having  crowns  used  to  supply  a  case,  like  the  one  just 
described,  on  perfectly  sound  teeth,  I  should  begin  by  using  an 
aluminum  disk,  with  corundum,  cutting  deep' as  possible,  both 
on  the  labial  and  lingual  sides.  Then  use  the  excising  forceps. 
This  can  be  done  under  the  influence  of  an  anesthetic,  or  other- 
wise. It  is  not  by  any  means  so  painful  an  operation  as  one 
would  think.  If  the  nerve  does  not  come  out  with  the  piece 
of  tooth  cut  off,  I  take  a  piece  of  orange  wood,  which  I  have 
previously  cut  the  proper  shape  to  drive  into  the  nerve  canal 
and  placed  in  creosote  a  few  minutes  before  beginning  to 
operate.  Immediately  after  severing  the  tooth,  drive  this 
into  the  canal,  then  remove,  and  dip  in  creosote  and  drive  in 
again.  This  vAU  perfectly  fill  the  nerve  canal  ;  all  sensitiveness 
will  disappear,  and  you  can  begin  to  operate  at  once.  I  do  not 
recommend  this  treatment  for  sound  teeth,  but  I  have  treated 
many  exposed  nerves  in  this  way ;  also,  many  teeth  broken  by 
accident,  and  think  this  the  most  satisfactory  way  to  dispose  ot 
such  cases.  I  have  never  had  any  unfavorable  results  follow 
after  operating  upon  teeth  in  this  way,  and  I  can  hardly  say  as 
much  in  favor  of  any  other  treatment.  I  speak  of  this  manner 
of  treating  exposed  nerves  as  one  of  the  operations  that  some- 
times becomes  necessary  in  adjusting  a  bridge  properly.  I  do 
not  claim  any  originality  in  this  mode  of  treatment.  I  know 
several  dentists  who  use  this  method,  all  of  whom  report  satis- 
factory results.  We  now  have  the  roots  prepared  to  receive  the 
case  as  shown  in  Fig.  411. 

"  I  have  many  of  these  cases  in  use  that  are  giving  entire 
satisfaction.     The  instrument  selected  for  preparing  these  roots 


342  MECHANICAL    DENTISTRY. 

should  be  one  with  small  inside  cutters  and  large  bevelers,  so 
as  not  to  cut  away  any  more  tooth-substance  than  necessary. 

"  Fig.  412  shows  the  case  ready  for  adjustment,  and  Fig.  413 
represents  the  case  after  adjustment. 

"  In  this  article  I  have  described  my  manner  of  making  teeth 

p^iG.  411. 


for  bridge-work.  I  am  now  having  made  a  tooth  expressly  for 
bridge-work  which  I  hope  to  be  able  to  place  on  the  market 
soon.     I  have   been    using   them,  but    have    not    perfected   my 

Fig.  412.  Ftg.  413. 


shells  and  molds  sufficiently  to  enable  me  to  get  them  out  in 
large  quantities. 

"  Fig.  414  shows   us    the   sockets,  which    I   propose   to    have 
ready  made  in  various  sizes,  in  bicuspids  and  molars. 


BRIDGE-DENTURES. 


343 


"Figs.  415  and  416  represent  the  shells,  which  are  to  be 
placed  in  their  positions  after  the  case  is  completed  and  ready 
for  adjustment. 

"  Fig.  417  represents  the  sockets  as  made  for  the  four  central 
and  two  cuspid  teeth.  The  advantage  of  these  teeth  can  readily 
be  seen,  not  only  for  bridge-work,  but  for  all-gold  plates.  A 
tooth,  if  broken,  can  readily  be  replaced  without  removing  the 
bridge  or  cracking  by  soldering,  and  at  small  expense. 


Fig.  414.  Fig.  415.         Fig.  416.  Fig,  417.         Fig.  418.        Fig.  419. 


^ 


"  Figs.  418  and  419  represent  the  teeth  placed  in  position." 
Dr.  Melotte's  Method.— Dr.  G.  W.  Melotte,  of  Ithaca,  N.  Y., 
contributed  to  the  Dental  Cosmos  an  account  of  his  method  of 
bridging  in  a  given  case,  the   manipulative  details  of  which  are 
here  reproduced  : — 

"  Fig.  420  illustrates  a  case  for  the  supply  of  a  lateral  and  a 
bicuspid.  In  this  instance  the  cuspid  should  be  cut  off,  and 
the  root  collared  and  capped  in  combination  with  a  pin  entering 
the  enlarged  pulp-canal ;  but,  as  there  may  be   grounds  for  ob- 

FiG.  420. 


jection  to  cutting  off  sound  teeth,  I  obviate  the  necessity  by 
cutting  a  shoulder  on  the  lingual  portion  of  the  cuspid,  and 
suitably  shaping  its  sides  to  permit  a  close  fitting  of  the  collar 
just  under  the  free  margin  of  the  gum.  A  narrow  strip  of  pure 
pattern  tin,  bent  tight  around  the  tooth-neck,  and  cut  through 
with  a  knife  at  the  lap  on  the  labial  surface,  will  serve  as  a 
measure  for  the  length  of  a  strip  of  22-carat  gold  plate,  No.  29 
thick,  and  as  wide  as  the  length  of  the  distal  side  of  the  cuspid. 


344 


MECHANICAL    DENTISTRY. 


The  ends  of  the  gold  are  then  squared,  and  with  round-nosed 
pliers  brought  evenly  together,  to  be  held  in  flush  contact  by  the 
soldering-clamp  shown  in  Fig.  421.  The  soldered  collar,  with 
its  joint  side  inward,  is  then  adjusted  on  the  tooth  as  accurately 
as  possible,  giving  slight  blows  with  a  mallet  until  the  collar 
touches  the  gum,  when  it  should  be  marked  to  indicate  the 
necessary  trimming  to  conform  it  to  the  gum  contour.  After  it 
has  been  thus  trimmed,  the  edges  beveled,  the  labial  part 
swelled  with  contouring  pliers,  and  the  lingual  part  cut  down  to 
about  one-tenth  of  an  inch  in  width,  the  collar  is  again  driven 
on,  and  will  appear  as  seen  in  Fig.  420.  A  stump  corundum 
wheel  is  then  used  to  grind  a  shoulder  on  the  lingual  surface  of 
the  tooth,  grinding  also  the  edges  of  the  collar  flush  with  the 
shoulder.     The  collar  is  again    removed,  and  a   piece    of  thin 

Fig.  421. 


platinum  plate,  about  No.  32,  sufficient  to  cover  the  lingual  sur- 
face of  the  tooth,  is  caught  on  the  lingual  edge  of  the  collar  by 
the  least  bit  of  solder,  and  all  put  in  place  on  the  cuspid  (see 
Fig.  422).  The  platinum  should  now  be  burnished  on  to  the 
shoulder,  and  over  the  tooth  and  collar  to  the  extent  shown  by 
the  lines  in  Fig.  422.  After  trimming  to  those  lines,  and  carefully 
replacing  and  burnishing  to  the  tooth,  the  collar  and  half  cap 
are  removed,  filled  with  wet  plaster  and  sand,  and  the  platinum 
soldered  to  the  gold.  It  is  then  placed  on  the  tooth,  burnished 
into  all  the  inequalities  of  the  tooth,  very  carefully  removed,  in- 
vested, and  enough  solder  flowed  over  the  platinum  to  cover  and 
give  it  strength.     Fig.  423  shows  it  complete  on  the  cuspid. 

"  I  have  feared  that  a  detailed  statement  would  imply  a  long 
and  tedious  process,  but  I  have  often  made  such  collars  in  less 


BRIDGE-DENTURES. 


345 


than  an  hour,  and  in  any  case  time  must  be  made  subservient  to 
exactness  of  fit  and  adaptation  to  the  end  in  view. 

"  In  the  preparation  for  fitting  a  collar  on  the  first  molar  (Fig. 
420)  I  should  have  wedged  or  otherwise  separated  it  from  the 
second  molar,  so  that  a  piece  of  sheet  brass  might  be  put  in  place, 
as  shown  by  Fig.  424,  and  an  impression  taken  in  plaster,  which, 
if  allowed  to  get  hard,  would  bring  away  the  metal.  If  not,  it 
could  be  replaced  in  the  plaster.  Melted  fusible  metal,  when 
near  the  cooling  point,  is  then  poured  into  the  impression,  and 
when  cold  will  allow  the  safe  removal  of  both  the  plaster  and 
the  metal  strip.  On  this  metal  model  a  collar  can  be  formed 
that  will  accurately  fit  the  molar,  as  seen  in  Fig.  420.  If  the 
molar  has  no  antagonist,  a  cap  may  at  once  be  struck  up  on  the 
model ;  but  if  there  be  an  antagonist  the  cusps  of  the  natural 
molar  should  be    removed    by    grinding    at  points    where  the 


Fig.  422.     Fig.  42 


Fig.  425. 


occluded  tooth  will  admit  of  sufficient  thickness  of  the  gold  cap. 
An  exact  copy  of  the  ground  cusps  can  then  be  made  in  less  than 
five  minutes  by  the  use  of  moldine  with  its  accessories,  see  page 
15  I,  and  the  process  is  as  follows  :  Make  the  tooth  perfectly  dry. 
Put  the  collar  on  it.  Nearly  fill  the  cup  with  moldine,  and 
coat  it  with  soapstone  powder.  Press  the  compound  on  the 
tooth  and  collar  firmly  to  about  one-fourth  the  depth  of  the 
tooth.  Carefully  remove  the  cup ;  trim  off  any  overhanging 
material,  and  place  the  rubber  ring  over  the  cup  to  about  one- 
half  the  depth  of  the  ring.  Melt  the  fusible  metal  and  pour  it 
as  cool  as  it  will  run  from  the  iron  ladle.  As  soon  as  the  metal 
is  hard,  remove  it  with  the  ring,  taking  care  not  to  impair  the 
impression,  which  can  be  used  again  if  the  die  is  found  imper- 
fect or  gets  injured  in  use.  Place  the  die  and  ring  in  cold  water, 
to  remain  until  quite  cooled.     While  the  die  is  wet  and  held 


34^  MECHANICAL    DENTISTRY, 

over  a  basin  of  water,  pour  into  the  ring  fusible  metal  which  has 
been  stirred  until  it  begins  to  granulate,  and  quickly  immerse  all 
in  the  water.  The  die  and  counter-die  should  separate  readily 
by  tapping  them  with  a  hammer,  but  if  they  stick,  others  can 
be  quickly  made  from  the  same  impression,  by  the  same  method, 
using  more  care.  With  this  die  and  its  counter-die,  a  piece  of 
No.  29  or  30  gold  plate  is  swaged  to  fit  perfectly  the  cusps  and 
collar,  which,  when  removed,  can  be  held  to  its  place  on  the  cap 
by  the  soldering-clamp,  using  spring  pressure  enough  merely  to 
hold  them  together  for  careful  soldering  with  the  pointed  flame 
so  as  not  to  unsolder  the  collar.  The  seamless  collars  are  excel- 
lent when  care  is  used  in  selecting  the  proper  size,  as  directed 
on  the  diagram. 

"  The  caps  being  in  place  on  the  cuspid  and  molar,  an  impres- 
sion is  taken  with  plaster,  the  caps  accurately  set  in  the  impres- 
sion, and  hard  wax  melted  with  a  hot  spatula  around  the  edges 
of  the  caps.  The  impression  is  then  thoroughly  coated  with 
sandarac  varnish,  after  which  it  is  dipped  for  a  moment  in  water 
and  filled  with  a  wet  mixture  of  one  part  marble-dust  with  two 
parts  of  plaster,  using  great  care  to  perfectly  fill  the  caps  and 
molds  of  the  teeth.  Wait  until  this  mixture  has  become  quite 
hard,  remove  the  cup,  and  with  a  suitable  knife  clip  off  the 
plaster  without  marring  the  cast ;  secure  a  good  articulating 
impression,  and  transfer  it  to  the  cast  to  obtain  an  exact  re- 
production of  the  relative  occlusions  of  all  the  teeth  involved. 
With  such  an  articulation  in  hand,  and  with  the  means  al- 
ready described  for  swaging  gold  or  platinum  plate  to  fit  the 
cusps  and  articulating  surfaces  of  either  the  natural  or  artificial 
teeth,  it  should  be  within  the  capacity  of  any  competent  dentist 
to  complete  a  suitable  bridge,  although  there  are  practical  points 
that  can  only  be  imparted  by  clinical  instruction  and  actual  de- 
monstration in  the  mouth.  Such  a  bridge  is  shown  in  position 
in  Fig.  425." 

Dr.  Parmly  Brown's  Method. — Dr.  E.  Parmly  Brown 
describes  a  process  of  bridging  which  is  characterized  as  "  All- 
Porcelain."  *     This  is  true  only  in  the  sense  that  no  metal  is 

*  Dental  Cosmos,  vol.  XXVIII. 


BRIDGE-DENTURES.  347 

visible,  all  parts  of  the  metal  framework  being  concealed  within 
the  body  of  the  porcelain.     The  method  is  thus  described : — 

"  Fig.  426  is  a  lateral  view  of  a  porcelain  crown,  with  a  plat- 
ino-iridium  pin  baked  in  position.  The  pin  has  great  strength  at 
the  neck  of  the  tooth,  where  the  strain  is  greatest,  the  porcelain 
of  the  tooth  extending  up  on  to  it,  to  increase  the  strength. 

"  Fig.  427  is  a  front  view  of  the  same  crown,  showing  by 
dotted  lines  the  form  which  the  metal  occupies  in  the  crown  to 
increase  the  strength  of  the  attachment,  and  prevent  the  pin 
from  approaching  the  surface  in  thin  teeth. 

"  Fig.  428  is  a  view  of  the  two-pin  bicuspid  crown,  which 
affords  a  pin  for  each  root  of  a  two-rooted  bicuspid,  the  staple 
form  of  the  pin,  shown  by  dotted  lines,  being  a  feature  of 
strength. 

"  Fig.  429  is  a  view  of  a  bicuspid  crown  with  the  two  pins 
pressed  together,  making  a  single  pin  for  the  one  root. 

FiG.  427.  Fig.  428.  Fig.  429. 


"  The  double  pin  in  the  bicuspid  crowns  prevents  the  loosening 
of  these  teeth  by  the  rotary  movements  of  mastication,  which  by 
means  of  the  two  cusps  exert  such  leverage  as  to  t^rn  and  break 
down  the  ordinary  crown  where  only  one  pin  is  used. 

"  My  bridge-work  system  has  the  metal  baked  invisibly 
through  the  body  of  the  teeth.  No  metal  shows  either  inside 
or  outside  of  the  dental  arch.  The  six  anterior  teeth  are  riveted 
to  the  platino-iridium  bar  by  the  ordinary  pins  of  plate  teeth, 
which  are  the  teeth  used  for  this  work.  The  bicuspids  and 
molars  are  prepared  by  grinding  a  slot  on  the  palatal  surfaces  of 
the  teeth.  The  bar  (which  is  squared  for  these  teeth,  instead 
of  being  flattened,  as  for  the  front  teeth)  is  inserted  into  this 
sroove  or  slot,  which  should  be  orround  with  a  thin  corundum- 


348 


MECHANICAL    DENTISTRY. 


wheel  to  fit  the  bar,  which  can  be  barbed  to  make  proper  impinge.- 
ment.  It  is  then  ready  to  receive  the  creamy  tooth-body,  which  at 
this  juncture  is  appHed  to  the  palatal  surface  of  all  the  teeth, 
completely  covering  the  metal  and  giving  the  natural  contour 
to  the  inner  surfaces.  A  little  of  the  tooth-body  is  allowed  to 
run  between  the  teeth,  uniting  their  approximal  surfaces. 

"  In  this  work,  when  cross-pin  teeth  are  used,  the  pins  will  be 
ground  out  in  most  cases ;  but  if  straight-pin  teeth  are  used  the 
pins  will  be  bent  over  the  bar.  I  will  give  a  few  illustrations  of 
the  many  ways  in  which  this  work  can  be  done. 

"  Fig.  430  *  is  a  view  of  a  platino-iridium  bar  baked  on  to  a 
plain  plate  tooth,  by  first  riveting  the  flattened  bar  on  the  pins, 
then  applying  tooth-body  to  the  back,  completely  covering  bar 
and  pins,  and  then  baking  in  continuous-gum  furnace.  The 
body  can  be  applied  readily  of  a  creamy  consistence,  and  after 

Fig.  430. 


being  held  a  moment  over  a  spirit-lamp  is  ready  to  be  put  on 
the  slide  and  baked. 

"  Cavities  or  fillings  are  usually  found  on  either  side  of  a  space 
made  by  the  loss  of  a  tooth  or  teeth  that  will  allow  the  insertion 
of  the  ends  of  the  metal  bar  and  the  thorough  impacting  of  gold 
around  them.  Amalgam  can  be  used  in  posterior  teeth  in  many 
cases,  or  gold  crowns  penetrated  by  the  bar,  as  in  Figs.  43 1  and 

432. 

"  In  Fig.  431,  No.  I   is  a  third  molar,  pulp  alive,  with  large 

*  "  Fig.  430  is  incorrect  in  two  respects.  The  palatine  aspect  of  the  completed 
l^icuspid  should  be  a  curved  line  from  the  palatine  cusp  to  the  cervico-labial  portion, 
and  not  make  a  saddle  over  the  ridge,  as  shown  in  the  cut,  which  would  be  non- 
cleansible.  The  other  cut,  with  a  bar  riveted  on  to  a  bicuspid,  should  have  the  bar 
placed  in  a  groove  ground  into  the  center  of  the  tooth,  riveting  being  done  to  incisors 
and  cuspids  only. " 


BRIDGE- DENTURES. 


349 


filling;  No.  2  is  a  porcelain  bridge  ;  No.  3  is  a  first  molar,  pulp 
dead,  with  a  metal  bar  entering  the  pulp  cavity. 

"  In  Fig.  432,  No.  I  is  a  second  molar,  pulp  alive,  with  the 
crown  filling  of  gold  or  amalgam  retaining  the  bar ;  No.  2  is  a 
porcelain  bridge;  No.  3  is  a  gold  crown  with  bar  passing  through 
crown  into  root. 

"  Fig.  433  is  a  view  of  a  bridge  of  two  teeth, — a  central  porce- 
lain crown  with  a  lateral  baked  into  it,  the  bar  and  pin  being 
of  the  same  piece,  bent  at  right  angles. 

"  In  Fig.  433,  No.  I  is  a  porcelain  crown  forming  part  of  the 
bridge ;  No.  2,  a  bridged  lateral  with  metal  bar  baked  through  it ; 
No.  3,  a  living  cuspid  with  a  metal  bar  running  in  the  center 
of  a  solid  eold  fillinsf. 


Fig.  43; 


Fig.  434. 


"  Fig.  434  is  a  view  of  a  central  incisor  bridged  on  to  two  teeth 
whose  pulps  have  been  lost. 

"  As  many  as  six  teeth  have  been  inserted  in  this  way  on  two 
central  roots,  and  the  posterior  end  of  the  invisible  metal  bar 
running  through  the  six  teeth  worked  firmly  into  a  gold  filling 
in  a  molar — the  six  teeth  being  united  on  their  approximal  sur- 
faces by  the  porcelain  running  between  them  at  the  baking. 
The  backs  of  such  teeth  must  be  given  a  curved  form  to  insure 
a  cleanly  condition. 

"  Fig.  435  is  a  view  of  the  attachment  of  the  bridge  to  a  tooth 
standing  alone,  where  the  tooth  has  a  gold  crown  attached,  or  the 
bar  is  worked  into  a  filling.  Nos.  i  and  3  are  teeth  on  a  por- 
celain bridge ;  No.  2  the  natural  tooth  over  which  the  bridge 
is  saddled. 


350  MECHANICAL    DENTISTRY. 

"  All  teeth  for  this  bridge-work  should  be  ground  so  that  no 
considerable  portion  of  gum  would  be  covered,  the  teeth  just 
touching  the  gum  by  a  point  only  at  the  cervico-labial  portion." 


REMOVADLE    BRIDGE-DENTURES. 

Dr.  Dexter's  Method. — Dr.  James  E.  Dexter,  in  a  paper 
read  before  the  First  District  Dental  Society  of  New  York, 
exhibited  models  and  submitted  descriptions  of  an  appliance 
which  he  denominated  the  "  Cap  Plate,"  which  is  removable 
from  the  mouth.  This  mode  of  substitution,  which  it  has  been 
claimed  was  tried  in  England  twenty  years  ago  and  abandoned 
as  injurious  to  the  teeth  capped,  is  intended  to  obviate  the 
objections  which  Dr.  Dexter  strenuously  asserts  attach  to  the 
ordinary  forms  of  bridge-work  permanently  fixed  in  the  mouth. 
Space  will  admit  of  only  such  parts  of  the  paper  as  relate  to 
the  mechanical  construction  of  the  appliance. 

"Leaving  now  bridge-work,  let  me  speak  of  cases  in  which  we 
could  (and  often  do)  wish  for  some  method  of  inserting  artificial 
substitutes  other  than  ordinary  plate-work.  Take  a  case  w^here, 
on  the  lower  jaw,  there  are  standing  in  the  mouth  a  third  molar, 
a  canine,  and  first  bicuspid,  on  each  side — six  teeth  in  all.  These 
teeth  are  shortened,  by  breakage  and  mastication,  so  that  the 
upper  incisors  close  to  within  an  eighth  of  an  inch  of  the  gum 
line  between  the  canines ;  added  to  this,  they  are  so  tipped  and 
twisted  in  their  places  as  to  make  it  very  difficult  to  properly 
adapt  an  ordinary  denture  to  the  space  between  them ;  and, 
lastly,  let  the  patient  evince  entire  abhorrence  of,  and  a  fixed 
resolution  not  to  permit,  the  resting  or  pressure  of  any  appliance 
upon  his  gum  tissues.  Such  a  case  is  the  one  for  which  I  have 
constructed  this  cap-plate.  Such  cases  are  often  treated  by 
building  up  or  down  the  natural  teeth  with  gold,  in  order  to  open 
the  bite,  and  then  replacing  the  lost  teeth  with  an  ordinary  plate. 
My  apparatus,  however,  accomplishes  both  these  desiderata  in 
one  operation,  while  simultaneously  avoiding  any  and  all  pres- 
sure upon  or  irritation  of  the  gum. 

"  The  appliance  which  I  now  show  you  (Fig.  436)  is  constructed 


BRIDGE-DENTURES. 


351 


as  follows  :  Caps  of  gold  and  platinum  alloy,  of  about  Nos.  26 
to  28  U.  S.  standard  gauge, 

are  struck   up   to   fit   over  Fig.  436. 

and  down  the  sides  of  the 
natural  teeth  selected  for 
the  piers,  fitting  closely. 
If  all  the  supporting  teeth 
stand  perpendicularly  and 
parallel  with  each  other, 
thus  creating  no  '  under- 
cut' (so  to  say),  the  sides 
of  the  caps  may  encircle 
the  teeth  as  far  as  possible 
{7iot,    however,    impinging 

upon  the  gum  line),  and  be  simply  slit  (in  tv/o  or  more  places  on 
each  tooth)  perpendicularly,  so  as  to  spring  apart  and  allow  of 
sliding  the  whole  over  the  natural  convexities  of  the  teeth,  the 
sides  coming  together  again  when  in  place,  and  thus  holding  the 
whole  apparatus  firm.ly.  But  should  the  teeth  be  tipped  or 
leaning,  and  not  parallel,  the  sides  of  the  caps  must  then  extend 
over  only  such  parts  as  can  be  closely  fitted,  and  yet  be  suffi- 
ciently perpendicular  and  parallel  to  allow  of  removal  and  re- 
placing of  the  appliance.  Of  such  a  character  is  the  case  now 
shown  you,  there  being  only  one  place  on  the  six  caps  where  a 
slit  is  of  value ;  the  sides  of  the  caps  being  so  fitted  as  to  hold 
partly  by  their  own  elasticity,  and  partly  by  that  of  the  whole 
apparatus.  Such  a  case,  of  course,  will  most  severely  try  the 
capabilities  of  any  artificial  denture ;  and  not  the  least  merit  of 
the  present  piece  is  its  triumph  over,  and  perfect  and  practical 
adaptation  to,  the  obstacles  of  an  exceptionally  difficult  case. 

"  The  caps,  when  struck  up,  will  not  cling  to  the  teeth  when 
in  place  ;  nor  should  they,  for  they  must  be  capable  of  easy 
removal  during  succeeding  processes.  But  when  the  piece  is 
ready  for  final  insertion,  the  sides  of  the  caps  must  be  sprung 
irnuard  sufficiently  to  hold  their  supports  with  firmness. 

"The  caps  being  now  made,  it  is  in  order  to  determine  the 
length  of 'bite'  needed.  Place  the  caps  in  position  in  the  mouth, 
and  build  wax  on  their  grinding  surfaces  to  a  proper  length  and 


352  MECHANICAL    DENTISTRY. 

contour,  both  side  and  grinding.  Invest,  remove  wax,  and  flow 
into  its  place  eighteen-carat  gold.  Shape  the  grinding  surfaces, 
by  trial  in  an  articulator  or  the  mouth,  to  the  proper  occlusion. 
Next,  take  an  impression  with  the  caps  in  place,  pour  the  model, 
select  and  back  plain  plate-teeth,  and  wax  them  in  place.  Invest 
the  whole,  remove  the  wax  from  the  backs  of  the  teeth,  and  fit 
in  the  spaces  between  the  caps,  bands,  or  bars  of  irido-platinum 
alloy  (or  gold,  as  circumstances  may  determine),  being  careful 
that  the  bars  fit  accurately  to  the  backings  of  the  porcelain  teeth 
and  to  the  caps  at  each  end.  In  fitting  the  bars  to  the  caps, 
select  such  points  of  attachment  as  will  not  interfere  with  the 
spring  of  the  slit  sides  of  the  caps.  If  necessary,  let  the  bars 
avoid  the  sides  of  the  caps,  and  reach,  by  curving,  to  the  tops  or 
grinding  surfaces.  Should  you  desire  to  arrange  the  porcelain 
teeth  irregularly,  you  need  not  hesitate  to  do  so.  Set  them  just 
as  you  would  for  rubber  or  celluloid,  and  then,  simply  taking  a 
'  finger  impression  '  of  their  backs  with  modeling  composition 
or  wax,  when  invested  as  above  stated,  and  making  dies,  you 
can  readily  '  strike  up  '  your  bars  to  fit  the  irregular  positions  of 
the  backings.  But  should  this  be  difficult,  on  account  of 
great  irregularity  or  stiffness  of  bars,  construct  the  bars  of  two 
or  three  thicknesses  of  metal,  each  struck  up  separately,  and 
'sweated'  into  one.  Next,  solder  the  bars  to  the  backed 
teeth,  but  not  to  the  caps  as  yet.  The  reason  is  that  perfect 
adaptation  of  the  bars  to  the  caps  is  absolutely  necessary  to  the 
success  of  the  piece.  Therefore,  now  place  the  caps  in  place  in 
the  mouth,  and  wax  the  bars  with  their  attached  teeth  in  the 
spaces  between  them,  filing,  grinding,  and  adjusting  until  all  is 
exactly  as  required.  Then  (and  not  until  then)  take  an  impres- 
sion of  the  whole  in  place,  the  apparatus  coming  away  with  the 
plaster.  Pour  the  impression  with'  plaster  pumice,  and  sand,  or 
asbestos  (sand  is  best),  carefully  remove  the  impression  plaster, 
invest  outside  the  model  with  its  sustained  apparatus,  and  then 
solder  the  caps  and  bars  together.  In  doing  this,  as  little  solder 
as  possible  should  be  used,  to  prevent  warping  of  the  whole. 
The  bars  should  have  a  broad,  firm  hold  on  the  caps  ;  but  the 
contour  of  their  union  should  be  made  on  the  bars  before  they 
are  united  to  the  caps,  and  not  by  flowing  on  a  body  of  gold 


BRIDGE-DENTURES.  353 

while  uniting  the  bars  and  caps  sufficient  to  attain  the  desired 
hold  and  shape  of  union.  On  the  contrary,  the  bars  should  be 
properly  shaped  at  their  ends,  and  carefully  fitted  to  the  surfaces 
to  which  they  will  be  attached,  when  a  small  amount  of  solder 
flowed  into  the  joint  will  make  a  perfect  union  and  give  all  the 
strength  possible.  All  that  now  remains  to  do  is  to  spring  or 
bend  slightly  inward,  as  before  directed,  the  sides  of  the  caps 
so  that  they  may  grasp  their  supporting  teeth  firmly,  yet  not 
too  much  so,  or  it  will  create  difficulty  in  removal  or  insertion ; 
then  finish  and  polish.  Burnishing  is  generally  objectionable, 
since  it  gives,  in  some  lights,  a  black  shine  to  the  piece,  adding 
greatly  to  the  prominence  of  the  appliance  as  a  part  of  the  view 
whenever  the  wearer  opens  his  mouth. 

"  Should  it  be  desired  to  produce  the  best  possible  results  with 
the  piece,  the  interstices  between  the  artificial  teeth  and  any 
other  crevices  to  be  found  may  be  filled  with  gold  or  amalgam 
— I  prefer  the  former;  or  vulcanite  may  be  packed  in  such 
places  (which  may  be,  if  necessary,  cut  out  to  proper  dimensions 
by  burring),  and  finished  up  smoothly.  The  piece  shown  you 
contains  no  less  than  seventeen  gold  fillings,  which  signifies  that 
no  debris,  or  even  moisture,  has  any  foothold  of  concealment 
about  it,  and  that  it  is,  therefore,  as  clean  in  itself  as  is  possible 
for  any  artificial  denture  to  be.  This,  you  will  say,  is  rather 
expensive  work.  Very  true.  The  whole  method  is  expensive 
in  both  money  and  labor.  But  I  am  quite  consoled  for  this  fact 
by  the  thought  that  it  will  not,  therefore,  be  likely  to  do  much 
harm  to  the  public,  since  the  '  cheap-jacks '  and  '  incompetents  ' 
will  probably  let  it  alone. 

"  In  the  piece  shown  there  are  six  caps,  three  on  a  side.  There 
are  five  incisor  teeth  placed  between  the  canines,  two  of  which 
are  capped  with  gold  to  break  up  the  uniformity  of  porcelain  in 
front,  as  contrasted  with  the  uniformity  of  gold  behind,  and  thus 
help  to  evade  artificiality  of  appearance.  Between  the  molar 
caps  and  the  double  caps  for  canine  and  bicuspid,  the  connecting- 
bar  is  horizontally  placed,  dipping  downward  to  parallel  the  gum 
line,  as  well  as  to  evade  an  encroaching  molar  above.  When 
necessary,  an  artificial  tooth  or  teeth  can  be  ground  and  soldered 
to  these  bars.  Generally,  however,  the  connecting  bars  should 
23 


354 


MECHANICAL    DENTISTRY. 


be  perpendicularly  placed,  to  insure  resisting  strength  in  the  line. 
of  the  attacking  force. 

"  Various  modifications  of  this  process,  as  regards  its  uses, 
will  at  once  suggest  themselves.  For  instance,  where  a  molar 
or  two  on  one  side  are  missing,  they  may  be  thus  artificially  re- 
placed without  a  plate,  provided  there  is  a  supporting  tooth  or 
teeth  at  each  end  of  the  space  ;  or  the  method  may  be  applied 
to  the  treatment  of  irregularity  by  capping  the  molars  and  bicus- 
pids, or  molars  alone,  connecting  the  caps  of  each  side  together, 
if  necessary,  by  a  band  or  strap  directly  across  the  roof  of  the 

Fig.  437. 


mouth,  or  curving  around  back  of  the  incisors.  To  these  bands 
or  straps,  or  to  the  caps  themselves,  hooks  or  buttons  for  attach- 
ment of  loops,  strings,  etc.,  or  threaded  nuts  for  use  with  screws 
may  be  soldered.  Should  it  be  desired,  for  instance,  to  'spread' 
the  bicuspid  region,  place  on  each  pair  of  these  teeth  a  cap  hav- 
ing a  socket  formed  on  its  inner  aspect,  and  let  the  ends  of  a 
'  Coffin  '  steel  spring  rest  in  these  sockets,  the  force  of  the  spring 
retaining  it  in  place,  and  the  teeth  alone  being  forced  apart  with- 
out pressure  on  the  gums.  This  is  applicable  to  a  single  tooth 
by  making  the  opposite  cap  enclose  teeth  enough  to  resist  back 


BRIDGE-DENTURES.  355 

pressure.  A  large  proportion  of  the  gum-irritation  usual  with 
treatment  of  irregularity  may  be  avoided  by  use  of  the  cap-plate 
instead  of  ordinary  plates. 

"  Should  it  be  desired  to  use  the  cap-plate  where  it  is  not  ad- 
visable to  open  the  bite,  the  caps  may  be  struck  and  fitted  as 
before  directed,  and  then  be  cut  through  and  aivaj  only  at  the 
points  of  occlusion,  leaving  the  balance  as  before.  In  doing  this, 
however,  be  sure  to  leave  enough  grinding  surface  to  the  caps 
to  securely  fasten  the  spring-sides  together. 

"This  method  is  eminently  applicable  to  cases  where  roots 
only  remain  in  the  mouth — provided  they  are  sufficient  in  num- 
ber and  strength  to  sustain  mastication.  The  variation  of  the 
process  here  required  is  simple.  Pivot  or  ferrule  permanently 
the  roots  by  any  proper  process  (the  Buttner  method  is  the  best 
in  this  case,  because  the  strongest) ;  but,  instead  of  mounting 
porcelain  teeth  on  the  pivots  or  ferrules,  fit  thereon  gold  piers  or 
stumps  of  a  proper  shape  (parallel-sided)  to  receive  the  caps  ; 
and  when  all  the  roots  are  so  mounted,  proceed  exactly  as  though 
the  metal  piers  were  so  many  natural  teeth, — capping  them  as 
such  (letting  the  caps  assume  the  form  and  size  of  teeth),  and 
fitting  connecting  bars  and  porcelain  teeth  into  the  interspaces. 
Root-cases  should  be  exceptionally  favorable  ones  for  this 
method,  since  the  piers  can  be  placed  exactly  perpendicular  to 
each  other,  and  be  so  shaped  as  to  secure  for  the  caps  the  best 
of  anchorage  and  bearing. 

Dr.  Starr's  Methods. — The  following  description  of  his 
methods  in  detachable  bridge-work  is  given  by  Dr.  R.  Walter 
Starr  :• — 

"The  case  of  Mr.  W.  presented  difficulties  of  an  unusual 
character,  as  may  be  seen  by  inspecting  the  illustration,  Fig. 
437,  which  renders  detailed  description  unnecessary. 

"  It  will  be  observed  that  the  molars  and  the  left  second 
biscuspid  overhang  to  a  degree  that  would  make  the  taking  of 
an  accurate  impression  by  ordinary  methods  well-nigh  impossible. 
After  a  careful  study  of  the  case,  it  was  decided  that  two  sepa- 
rate pieces  of  removal  bridge-work  should  be  attempted,  and, 
as  an  essential  preliminary  step,  the  overhanging  sides  of  the 
molars  and  bicuspids  were  ground  with  engine  corundum-wheels 


356 


MECHANICAL    DENTISTRY. 


<, 


and  points  until  those  sides  were  made  much  less  inclined,  when 
plaster  impressions  were  taken,  first  of  one-half,  and  then  of  the 
other  half,  of  the  jaw.  Gold  cap  crowns  were  closely  fitted  over 
the  molars,  left  second  bicuspid,  right  first  bicuspid,  and  cuspid 
stump.  Gold  crowns  were  made  to  telescope  over  all  the  caps, 
which  were  then,  by  means  of  oxyphosphate  cement,  fixed  firmly 
on  the  teeth.  Suitable  plate-teeth  were  selected,  fitted,  backed, 
and  waxed   in   place   between   the   telescoping   crowns.      After 


Fig.  438. 


hardening  the  wax  with  cold  water  from  a  tooth-syringe,  the 
pieces  were  carefully  removed,  invested,  and  soldered.  The  two 
completed  bridges  were  easily  replaced  on  or  removed  from  the 
supporting  capped  teeth,  and  their  appearance  when  detached  is 
correctly  shown  by  the  illustration.  Fig.  438,  which  also  shows 
the  capped  teeth  and  stumps.  This  figure  likewise  shows  the 
results  of  the  novel  method  employed  in  crowning  the  incisors. 
Gold  collars  were  fitted  tight  on  the  necks  of  the  incisor  stumps, 
and  the  new  style  porcelain  caps  adjusted  in  the  collars,  and  set 


BRIDGE-DENTURES. 


357 


in  the  oxyphosphate  cement  which  had  been  packed  into  the 
collars ;  thus  at  the  same  time  fastening  the  collars  on  the 
stumps  and  the  caps  in  the  collars. 

"  Fig.  439  illustrates  the  finished  crowns  and  bridges,  which 
latter  were  secured  in  position  by  placing  a  small  piece  of  gutta- 
percha in  each  of  the  telescoping  cap-crowns,  which  were  then 
warmed  and  carefully  pressed   in   place — the  gutta-percha  filling 


Fig.  439. 


I 


only  the  spaces  between  the  flat  tops  of  the  caps  of  the  natural 
teeth  and  cuspid  caps  of  the  bridges. 

"  Whenever,  for  repair  or  for  any  other  purpose,  it  shall  be- 
come desirable  to  remove  one  of  the  bridges,  that  may  readily 
be  done  by  applying  a  hot  instrument  or  hot  air  to  the  caps  to 
soften  the  gutta-percha  sufficiently  to  permit  the  telescoping 
bridge  to  be  taken  off. 

"  A  full  upper  vulcanite  denture  was  made  to  replace  the  old 
one,  which,  by  improper  occlusion,  had  thrown  the  full  force  of 
mastication  on  the  anterior  teeth  of  the  lower  jaw,  and  produced- 


358 


MECHANICAL    DENTISTRY. 


the  destructive  action   that  resulted   in   the   deplorable   loss  of 
tooth-substance  shown  in  Fig.  437."* 

The  next  case  also  presented  unusual  difficulties,  "  The 
forward  overhang  of  the  inferior  right  second  molar  was  so  ex- 
cessive that  an  impression  could  hardly  be  taken,  until  with  co- 
rundum-wheels and  points  the  sides  of  the  tooth  had  been  made 
parallel,  or,  rather,  slightly  tapering,  to  form  a  truncated  cone, 
with  the  neck  as  a  base.  The  molar  was  alive  and  sound,  but 
the  crown  was  gone  from  the  pulpless  cuspid,  which  I  suitably 
shaped  by  means  of  my  root-trimmers  (Fig.  440). 


Fig.  441. 


"  An  impression  was  then  taken,  the  cast  from  which  is  illus- 
trated by  Fig.  441.  A  seamless  gold  collar  was,  by  means  of  a 
slightly  tapering  mandrel,  made  to  exactly  fit  the  tapered  nat- 
ural molar,  the  lower  edge  of  the  collar  cut  to  conform  to  the 
gingival  margin,  a  cap  piece  of  gold  plate  soldered  to  the  top 
edge  of  the  collar,  and  a  hole  drilled  through  the  center  of  the 
completed  cap  (A).  Care  was  taken  to  so  fit  and  proportion  the 
cap  that  it  would  require  finally  pretty  hard  driving  to  send  it 
home  on  the  tooth  ;  but  first  there  was  fitted  to  the  cap  a  tele- 


*  Dental  Cosmos,  vol.  xxvni.  No.  i,  page  17. 


BRIDGE-DENTURES. 


359 


scoping  seamless  collar,  on  which  was  soldered  a  gold  plate, 
with  cusps,  to  form  a  molar  crown  as  shown.  The  molar  was 
then  thoroughly  dried,  slightly  painted  with  agate  cement,  and 
the  cap.  A,  driven  hard  down  with  a  flat  pine  stick  held  upon  it 
and  struck  with  a  mallet,  the  hole  in  the  cap  enabling  me  to  see 
when  the  cap  was  quite  down.  The  cuspid  was  then  likewise 
fitted  with  a  seamless  gold  collar,  the  top  edge  of  which  was 
given  a  roof-shape,  as  seen  above  the  root  in  Fig.  441.  A  piece 
of  gold  received  a  corresponding  roof-shape,  had  a  short  section 
of  gold  tubing  soldered  into  it,  and  was  trimmed  to  the  outline 
of  the  collar,  beside  which,  B,  its  form  is  seen,  and  to  which  it 
was  subsequently  soldered,  after  suitable  investment  to  keep  the 

Fig.  442. 


parts  in  proper  place.  The  root-canal  had  been  previously  pre- 
pared to  receiv^e  the  tube,  which,  with  its  roofed  cap,  was  with 
stick  and  mallet  driven  hard  down  over  the  root.  A  piece  of 
gold  wire  exactly  fitting  the  tube  had  a  roof-shaped  piece  of 
properly  perforated  gold  plate  slipped  over  it  into  position  on 
the  root ;  became  fixed  in  such  relation  by  a  drop  of  melted 
hard  wax;  was  removed,  invested,  soldered,  and  finished  in  such 
shape  that,  excepting  the  hollowness,  it  looked  like  the  tube  and 
cap  B. 

"  The  relations  of  the  occluding  teeth  had,  of  course,  been  de- 
termined by  an  articulating  model,  and  by  means  of  it  a  series 
of  seamless  gold  collars  and  cusp-crowns  were  adjusted  on  a 
thin  platinum  plate  fitted  on  the  cast  between  the  cuspid  and 
second  molar,  and  the  collars  soldered  to  the  plate  after  invest- 


360  MECHANICAL    DENTISTRY. 

ment.  The  truss  thus  formed  received  an  appropriate  finish  by 
the  rounding  and  smoothing  of  its  basal  borders.  A  plain  plate  ' 
cusjDid  was  backed  with  gold  plate  and  fitted  on  the  roof-plate, 
to  which,  after  determining  its  proper  occlusion,  it  was  secured 
by  hard  wax,  removed,  invested,  and  soldered.  It  was  then  put 
into  the  tube  on  the  root,  the  telescoping  cap  put  over  the 
molar,  the  truss  put  in  position  in  the  mouth,  and  the  whole 
covered  with  plaster  and  marble-dust,  contained  in  a  suitable 
sectional  impression-tray,  which  enabled  me  to  hold  the  mass 
steadily  in  place  until  the  mixture  was  sufficiently  hard  to  bring 
away  cap  and  truss  and  roof-plate  all  in  proper  position.  A 
second  mixture  of  plaster  and  marble-dust,  and  a  suitable  trim- 
ming of  the  first  mixture  after  all  was  hard,  sufficed  for  the  sol- 
dering process  that  resulted  in  the  denture  which,  when  finished, 
appeared  as  shown  detached  at  C,  Fig.  441,  and  mounted  on  the 
cast  in  Fig.  442.  It  went  firmly  to  place  in  the  mouth,  and  yet 
was  removable  in  the  possible  event  of  accident  to  the  denture, 
or  for  readjustment  of  the  cusp-crowns,  which  latter  could  easily 
be  done  by  warming  the  piece  sufficiently  to  soften  the  gutta- 
percha, replacing  the  denture  on  its  anchorages,  and  directing 
the  proper  closure  of  the  occluding  teeth." 

Dr.  Parr's  Method. — The  following  is  Dr.  H.  A.  Parr's 
method  of  constructing  removable  bridge  dentures.  In  describ- 
ing it*  the  Doctor  says  : — 

In  the  construction,  adjustment,  and  placing  of  a  dental  sub- 
stitute, one  of  the  first  considerations  is  its  immovability  in 
position,  and  next  its  removability  for  cleansing  or  repair.  The 
old  styles  of  clasp-dentures  met  these  two  essential  requirements 
when  the  forms  and  relations  of  the  supporting  teeth  were  such 
that  the  clasps  would  firmly  embrace  those  natural  teeth  and 
hold  the  close-fitting  plates  in  position.  But  the  clasped  teeth 
soon  became  worn  or  wasted,  and  in  consequence  the  loose 
denture  lost  its  efficiency.  Even  in  favorable  cases  the  inverted 
cone  shape  of  nearly  every  natural  tooth  made  it  a  matter  of 
difficulty  to  secure  at  the  neck  near  the  gum  a  tight  fit  of  the 
springy  clasp,  which,  in  every  instance,  must   have   been   large 

*  Dental  Cosmos,  vol.  XXXI,  page  172. 


BRIDGE-DENTURES. 


^6  I 


enough  to  go  over  the  crown  of  the  supporting  tooth.  Then, 
too,  there  was  the  tendency  of  the  plate  to  press  into  the  gum 
and  so  become  loose  by  carrying  the  clasp  to  a  yet  narrower  place 
on  the  tooth.  In  many  cases,  moreover,  the  supporting  teeth 
inclined  toward  or  away  from  each  other,  and  made  it  well-nigh 
impossible  to  construct  a  plate  which  could  be  sprung  into  place 
and  yet  so  tightly  clasp  the  teeth  as  to  firmly  hold  the  denture 
in  position. 

The  object  in  devising  the  method  of  attachment  and  organiza- 
tion of  dental  substitutes  now  to  be  explained  was  to  avoid  the 
difficulties  mentioned,  as  will  be  made  evident  in  the  following 
description  of  two  practical  cases. 

Fig.  443. 


Fig.  443  is  from  the  plaster  cast  of  a  lower  jaw  in  which  onl}^ 
the  lower  left  second  molar,  cuspid,  and  right  first  bicuspid 
remained.  The  molar  and  bicuspid  were  fitted  with  gold  cap- 
crowns.  Gold  sockets  were  prepared,  and  gold  tongues,  made 
of  strips  of  spring  gold  plate  having  their  ends  folded  upon 
themselves  to  form  spring  catches,  were  fitted  to  the  sockets. 
The  cap-crowns  were  placed  on  the  plaster  teeth,  the  boxes  or 
sockets  hard  waxed  to  the  sides  of  the  crowns,  and  the  tongues 
hard  waxed  to  a  piece  of  stiff  wire  so  that  the  two  tongues  could 
be  lifted  out  of  their  sockets  without  breaking  either  the  tongues 
from  the  wire  or  the  sockets  from  the  crowns.  When  by  re- 
peated trials  this  could  be  done,  the  crowns  and  sockets  were 
taken  from  the  cast,  invested  in  plaster  and  marble-dust,  and  the 


362 


MECHANICAL    DENTISTRY. 


sockets  soldered  to  the  crowns.     These  were  replaced  upon  the 
cast  and  appeared  as  seen  in  Fig.  443. 

The  tongues  were  then  placed  in  the  sockets,  the  artificial 
teeth  arranged  on  the  cast  and  waxed  up  as   usual  for  vulcanite 

Fig.  444. 


work,  taking  care  that  the  projecting  ends  of  the  tongues  were 
so  embedded  in  the  wax  that  they  would  be  held  firmly  when 
the  piece  should  be  removed  to  be  flasked.  It  is,  in  fact,  best  that 
at  the  outset  the  tongues  should  be  soldered  to  a  stout  gold 
wire  bent  to  fit  the  cast,  so  that  the  wire  will  stiffen  the  waxed- 


FiG.  445. 


up  piece,  and  also  hold  the  tongues  more  securely  in  the  piece 
during  and  after  vulcanization. 

Fig.  444  shows  the  vulcanized  denture  in  place  on  the  cast. 

The'underside  of  the  denture  is  shown  in  Fig.  445,  which  also 
makes  evident  the  forms  and  relations  of  the  toneues  which  hold 


BRIDGE-DENTURES. 


363 


Fig.  447. 


the  denture   in  place.     The  paralleHsm  of  the  tongues  permits 

their  ready  removal   from  their  sockets,  no  matter  how  much 

awry  the  supporting  teeth  may  P         , 

be.    The  bearing  of  the  denture 

upon  the  cap-crowns  admits  of 

the  contact  of  the  denture  with 

the  gum  on  which  it  rests  but 

cannot  be  pressed  into  because 

of    the     cap-crown     supports. 

The  original  denture  of  which 

this   is   a   duplicate  is    now   in 

satisfactory  use. 

Fig.  446  represents  the  artic- 
ulated cast  of  a  case  for  which 
a  similar  tongue  and  clasp 
vulcanite  denture  was  made. 
This  is  illustrated  in  Fig.  447, 
which  needs  no  description. 
Fig.  448  shows  the  denture  in 
place,  the  original  having  been 

made  for  and  placed  in  the  mouth  of  a  patient  exhibited  at  the 
clinic  of  the  Odontological  Society  of  Pennsylvania,  at  Phila- 
delphia, in  December,  1888. 

These  are  simple  examples  of  a  class  of  work  having  a  wide 
range  of  application  and  capable  of  construction  without  the 
trouble  and  cost  of  all-gold  plate-Work. 

The  sockets  and  spring  tongues  require  some  skill  and  nicety 
of  workmanship  to  insure  a  close  fit  of  the^one  in  the  other  so 
that   the   attachment  shall    be 


firm,   yet    capable    of  easy-de- 
siened  detachment  for  cleans- 


FiG.  44S. 


mg  or  repair. 

A  notable  advantage  of  this 
mode  of  constructing  dentures 
for  the  upper  jaw  is  manifest 
in  the  fact  that  the  surface  of 
the  plate  which  rests  upon  the 
gums  need  only  be  wide  enough   to  cover  the   ridge,  and  thus 


364  MECHANICAL    DENTISTRY. 

avoid  the  quite  too  common  interference  of  artificial  dentures 
with  the  functions  of  taste  and  speech. 

Dr.  Davenport's  Method. — The  following  method  of  con- 
structing partial  dentures,  described  by  Dr.  J.  L.  Davenport  in 
the  Dental  Cosmos,  is  an  amplification  of  the  principle  of  attach- 
ment involved  in  the  process  just  considered. 

The  case  treated  by  Dr.  D.  was  one  where  the  only  teeth  re- 
maining in  the  upper  jaw  were  the  six  front  teeth,  the  three 
molars  on  the  right  side,  and  the  first  bicuspid  on  the  left.  The 
crowns  of  the  front  teeth  were  wholly  obliterated  from  excessive 
attrition    consequent  on    the  loss  of  the  occluding  back  teeth 

Fig.  449. 


■1,;  '^^^  'im$m    - 

"  ■  "!'ii'iv"(|i|ii|ri'n'  '   •!  ■  ''rfmmiMmfi'  WM'" ' 

necessitating  the  exclusive  use  of  the  former  in  mastication, 
as  shown  in  Fig.  449.  The  shortening  of  the  lower  teeth,  re- 
sulting from  the  same  cause,  was  remedied  by  building  them  up 
to  a  uniform  height  with  crystal  gold,  Fig.  453,  the  vacuities  in 
the  lower  jaw  resulting  from  the  loss  of  the  left  central  incisor 
and  several  of  the  back  teeth  being  supplied  with  substitutes  in 
the  manner  hereinafter  described. 

For  this  case  what  is  termed  a  "  Combination  Plate  and  Mov- 
able Bridge  "  was  constructed,  and  is  thus  described  : — 

"  The  two  superior  cuspid  roots  were  dressed  down  nearly  to 
the  gum,  and  fitted  with  22-carat  gold  cap-crowns,  similar  to 
those  described  by  Dr.  J.  Rollo  Knapp.  After  these  had  been 
placed  in  position,  a  hole  was  drilled  through  each  cap  of  a  size 


BRI DGE-DENTURES. 


36: 


suited  to  that  of  the  pulp  canal,  and  a  tube  of  iridium  and 
platinum  was  adjusted  in  the  root  cap  and  waxed  in  position. 
The  cap  and  tube  were  then  taken  off  and  soldered,  great  care 
being  taken  to  have  the  tubes  enter  both  roots  perfectly  parallel. 
These  were  permanently  secured  in  the  roots  with  gutta-percha, 
and  to  prevent  the  caps  being  pulled  off,  the  top  of  each  tube 
was  slit  down  a  trifle,  and  after  insertion  was  bent  back  into  the 
gutta-percha  with  a  warm  instrument. 

"  The  incisor  roots  having  been  dressed  down  even  with  the 
gum  and  filled,  a  plaster  cast  was   taken  and  a  narrow  20-carat 

Fig.  450. 


gold  plate  was  swaged  to  fit  over  the  ends  of  the  incisors  and  the 
capped  cuspids,  making  it  a  little  broader  where  it  had  to  rest 
on  the  gum  back  of  the  first  left  bicuspid  root.  A  hole  in  the 
plate  was  then  made  to  expose  the  root  of  the  first  left  bicuspid. 
This  was  fitted  with  a  bifurcated  iridio-platinum  pin,  having 
notched  sides,  and  a  hammered  head  upon  its  lower  end,  which 
came  down  below  the  root  about  three-eighths  of  an  inch. 

"A  thin  iridio-platinum  band  was  then  made  to  encircle  the 
root,  passing  just  under  the  gum  and  being  slightly  longer  than 
the  headed  pin.  This  band  was  perforated  with  two  rows  of 
holes,  from  without  inward,  giving  the  inner  surface  a  rough- 
ness similar  to  that  of  a  nutmeg-grater.     The  band  and  pin  were 


366  MECHANICAL    DENTISTRY, 

then  made  secure  to  the  root  with  a  non-shrinkable  copper 
amalgam. 

"  Fig.  450  shows  the  upper  jaw  ready  for  the  plate. 

"  I  must  mention  here  that  this  method  of  lengthening  the  bi- 
cuspid is  not  original  with  me,  but  has  been  previously  described 
by  Dr.  E.  Parmly  Brown.  I  have,  however,  used  this  method 
several  times  on  very  frail  roots,  and  cemented  over  the  entire  a 
gold  cap-crown. 

"  In  the  present  case,  after  the  amalgam  had  become  hard  and 
the  end  and  sides  had  been  polished,  a  gold  crown  was  fitted 
over  all  just  up  to  the  margin  of  the  gum,  and  in  close  contact 
with  the  end  of  the  band  and  amalgam.  This  crown  was  loose 
enough    to    admit   of  its   sliding  on  and   off,  though  with  just 

Fig.  451. 


enough  friction  to  hold  it  in  place  when  at  rest.  This  gold 
crown  was  then  placed  in  position,  the  plate  also  inserted,  and 
hard  wax  used  to  firmly  join  the  two  in  the  mouth.  They  were 
then  removed  and  soldered. 

"  Gold  pins  were  then  placed  through  holes  drilled  in  the 
plate  into  the  tubed  cuspids ;  then  soldered  to  the  plate,  the 
pins  being  of  a  size  to  fit  the  tubes  accurately.  The  plate  was 
also  provided  with  a  wide  clasp  encircling  the  first  molar  on  the 
right. 

"  The  plate  was  then  provided  with  a  gold  bar  about  one-eighth 
of  an  inch  wide,  occluding  perfectly  with  the  lower  teeth,  and 
plain  teeth  soldered  in  place,  hiding  the  bar,  and  just  meeting 
the  gum  in  front  of  the  incisor  roots.  The  plate  rested  squarely 
against  the  capped  cuspids,  each  of  which  showed  a  narrow  band 


BRIDGE-DENTURES.  367 

of  gold  when  the  plate  was  in  position.  As  finally  completed 
(see  Fig.  451),  this  was  the  most  perfectly- fitting  piece  I  ever 
inserted,  requiring  great  care  in  its  removal,  and  yet  by  a  little 
practice  the  gentleman  was  able  to  remove  and  replace  it  quite 
easily.  It  was  also  as  firm  as  any  permanent  bridge  could  have 
been,  though  it  had  no  support  on  the  left  side  back  of  the  first 
bicuspid. 

"  The  lower  jaw  was  supplied  with  a  double  20-carat  gold  plate, 
having  a  wide  clasp  on  the  first  right  bicuspid,  which,  after  being 
built   up,  presented  a  cone-shaped  top,  about  which  the  clasp 

Fig.  452. 


fitted  so  as  to  rest  firmly  upon  the  end  of  the  tooth,  thus  pre- 
venting injury  to  the  gums  during  mastication. 

"  The  only  other  peculiarity  was  that  the  second  left  inferior 
molar,  being  abnormally  short,  though  well-formed  and  standing 
upright,  was  fitted  with  a  wide  clasp,  extending  about  one- 
eighth  of  an  inch  about  the  tooth,  and  a  piece  of  gold  plate 
with  gold  cusps  was  soldered  into  its  clasp,  covering  the  molar 
crown,  and  occluding  with  the  molar  on  the  upper  plate.  (See 
Fig.  452).  This  not  only  prevented  the  plate  from  being  bitten 
down  unpleasantly  on  the  gums  during  mastication,  but  enabled 
me  to  use  a  shorter  molar  upon  the  upper  than  I  otherwise 
could  have  done,  and  better  allowed  the  antero-posterior  and 
lateral  movements  of  the  jaws. 

"  Fig.  453  shows  the  case  as  completed." 

The  Mandrel  System. — The  following  description  of"  A  Sys- 


568 


MECHANICAL    DENTISTRY. 


tern  of  Crown-  and  Bridge-work  "  is  given  by  the  experts  of  the 
S.  S.  White  Manufeicturing  Co.,  who  have  designated  it  as  "  The 
Mandrel  System." 

"An  examination  of  a  large  number  of  human  teeth  shows 
that,  no  matter  how  great  differences  may  exist  in  the  apparent 
shapes  of  the  crowns  of  individual  teeth  of  a  given  class,  there 
is  a  remarkable  uniformity,  in  the  configuration  of  their  necks. 
That  is,  the  necks  of  upper  cuspids,  for  instance,  were  found  to 
have  a  fixed  type,  from  which  the  variations  were  very  sHght  as 
to  shape,  though  there  appeared  to  be  no  exact  standard  of  size. 
So  of  the  other  classes,  with  the  single  exception  of  the  superior 


Fir..  4S3. 


'liii 


molars,  in  which  tvvo  distinct  forms  were  found,  the  first  being 
those  in  which  the  buccal  roots  were  wider  than  the  palatal ;  the 
second,  those  in  which  the  reverse  condition  was  found,  the  sin- 
gle palatal  root  being  wider  at  its  junction  with  the  crown  than 
the  two  buccal  roots.  The  occurrence  of  roots  of  the  second 
class  being  rather  exceptional,  the  first  class  was  accepted  as  the 
type. 

"The  configuration  of  the  necks  of  all  the  teeth  having  been 
determined,  a  set  of  mandrels  for  shaping  collars  to  fit  them  was 
devised.  The  set  (Fig.  454)  consists  of  seven  mandrels,  six  of 
which  are  double  end.  Their  shapes  are  modeled  upon  the 
general  typal  forms  of  the  necks  of  the  teeth  which  they  repre- 
sent, and   they  are  made  tapering  to  provide  for    all  required 


Fig.  454. 
MANDRELS 

FOR  SHAPING  SEAMLESS  TOOTH-ROOT  COLLARS. 


Wo.  8. 


370  MECHANICAL    DENTISTRY. 

variations  in  size.  The  illustrations  are  about  two-thirds  actual 
size,  the  longest  instruments  being  nine  inches  in  length.  The 
cross-sections  show  the  shapes  and  proportionate  sizes  at  the 
greatest  and  least  diameters.  The  long  taper  permits  the  most 
minutely  accurate  adjustment  of  the  collars. 

"  No.  I  is  a  double-end  mandrel,  for  superior  molars,  right  and 
left;  No.  2  is  a  single  mandrel,  for  superior  bicuspids,  right  and 
left ;  No.  3  is  a  double-end,  for  superior  cuspids,  right  and  left ; 
No.  4,  double-end,  for  superior  centrals,  right  and  left;  No.  5, 
double  -end,  for  inferior  molars,  right  and  left;  No.  6,  double-end, 
for  the  inferior  centrals,  laterals,  cuspids,  and  first  bicuspids,  right 
and  left;  No.  7,  double-end,  one  end  for  the  superior  lateral  in- 
cisors, the  other  for  those  bicuspids  in  which  a  bifurcation  of  the 
roots,  or  a  tendency  in  that  direction,  extends  across  the  neck  to 
the  crown  in  the  form  of  a  depression  on  one  or  both  approxi- 
mal  surfaces.  The  foregoing  scheme  comprehends  all  the  teeth 
of  the  permanent  set  except  the  second  inferior  bicuspids.  The 
necks  of  these  approximate  those  of  the  superior  central  incisors 
so  closely  in  shape  that  it  was  deemed  inexpedient  to  make  a 
separate  mandrel,  as  the  No.  4  mandrel  will  serve  for  both. 

"  The  collars  or  bands  are  made  seamless,  of  No.  30  (Ameri- 
can gauge)  gold  plate,  22  carats  fine.  Fifteen  sizes,  each  of  three 
widths  (-jIq,  3^q,  and  -^  inch)  are  made  (Fig.  456),  which  it  is  be- 
lieved will  cover  all  requirements.  These  collars,  although 
devised  as  a  part  of  the  system,  can  be  used  in  all  methods  of 
crown-  and  bridge-work  which  require  bands,  and  possess  many 
advantages  over  any  others.  They  are  really  labor-saving  de- 
vices, as  their  use  saves  the  time  and  trouble  of  making,  and 
there  is  no  danger  of  their  coming  unsoldered  when  the  pins  or 
the  backing  of  the  crown  are  being  soldered ;  and  there  are  no 
hard  spots  to  give  trouble  in  burnishing,  as,  for  instance,  close 
to  the  root,  after  the  collar  has  been  shaped  and  placed  in  posi- 
tion, the  whole  surface  being  uniformly  soft. 

"  The  seamless  collars  are  also  especially  adapted  to  remov- 
able or  detachable  bridge-work.  They  are  so  constructed  that 
Nos.  I,  16,  and  31  exactly  fit  into  or  telescope  with  Nos.  2,  17, 
and  32,  and  so  on  through  the  entire  set,  each  collar  fits  into  the 
series  next  higher;  so  that  a  root  may  be  banded  with  one  size 


BRI DGE-DENTURES. 


3/1 


and  the  size  next  larger  used  to  form  the  tube  for  the  telescoping 
crown.  When  desirable,  the  '  seamless  '  collar  can  be  strength- 
ened, after  it  has  been  adapted  to  the  conformation  of  the  crown 
so  as  to  slide  freely  over  it,  by  inv^esting  and  flowing  solder  over 
the  outer  surface ;    or,  still  better,  by  adapting  the  next  larger 

Fig.  455. 


size  of  collar  to  exactly  fit  around  the  first,  and  then  investing 
the  two  and  soldering  them  together.  The  advantages  of  these 
collars  for  this  kind  of  work,  and  also  for  the  construction  of 
cap-crowns,  are  obvious. 

"  The  other  appliances  specially  devised  for  this  system  are,  a 
reducing  plate  or  contractor,  a  pair  of  collar  pliers,  and  a 
hammer. 


Fic.  456. 


( 


o 
o 

o 
o 
o 

o 


W5 


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9i 


GO 


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M 


W 


V^ 


J 


D 

2D 


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s  (D 


BRIDGE-DENTURES. 


1  '7  T 


"  The  contractor  (Fig.  455)  contains  holes  which  are  comple- 
mentary in  shape  to  the  mandrels.  The  mandrels  being  applied 
to  the  inner  circumferences  of  the  collars,  while  the  contractor 
must  admit  the  collars  themselves,  the  short  taper  of  the  holes 


in  the  contractor  necessarily  covers  a  somewhat  greater  range  of 
size  than  is  shown  in  the  mandrels.  With  this  appliance  collars 
can  be  evenly  and  accurately  reduced  in  size  at  the  edges,  with- 
out burring  or  buckling.     The  illustration  is  actual  size. 


374 


MECHANICAL    DENTISTRY. 


Fig.  458. 


"  The  collar  pliers  (Fig.  457)  are  for  contouring  the  collars  to 
shape,  one  beak  being  made  convex  and  the 
other  concave  to  correspond.  With  this  appli- 
ance the  slightest  changes  required  in  the  con- 
tour of  the  collars  are  easily  made.  About  a 
half-inch  from  the  extremity  of  the  concave 
beak  a  small  bar  of  flat  steel  is  attached  to  it 
by  means  of  a  screw.  The  free  end  of  fehe  bar 
has  a  minute  projection  upon  one  face,  the  other 
being  reinforced  to  fit  into  the  concavity  of  the 
beak.  In  the  center  of  the  face  of  the  convex 
beak  is  a  depression,  into  which  the  projection 
on  the  steel  bar  strikes,  making  a  very  efficient 
punch  for  forming  guards  or  stops  to  prevent  the 
collars  from  being  forced  too  far  under  the  gum. 
The  depression  in  the  convex  beak  being 
slightly  larger  than  the  projection  or  punch, 
the  metal  is  not  cut  through,  but  merely  raised 
on  the  side  opposite  to  the  punch.  The  punch 
attachment  being  pivoted  can  be  swung  to  one 
side  when  not  in  use. 

"Fig.  458  is  a  mallet  or  hammer,  with  steel 
face  and  horn  peen.  The  handle  is  nine  inches 
long. 

"  One  of  the  appliances  required  is  a  lead 
anvil,  which  being  onh'  a  piece  of  soft  lead,  say 
two  by  three  inches,  and  an  inch  thick,  is  not 
illustrated.  The  counter-die  of  an  ordinary 
case  will  answer  very  well. 

"To  illustrate  the  uses  of  these  appliances, 
take  a  case  in  which  the  two  inferior  bicuspids 
of  the  left  side  are  missing,  and  the  crowns  of 
the  cuspid  and  first  molar  so  badly  deca}"ed  that 
the  probabilities  are  that  the\-  will  soon  fall 
victims  to  the  forceps.  The  old-time  way 
would  have  been  to  extract  the  molar  and  cus- 
pid, and  make  a  partial  plate.  E.xamination,  however,  shows 
that  the  roots  of  these  two  teeth  are  in  good  condition,  afford- 


BRIDGE-DENTURES.  375 

ing  an  excellent  opportunity  for  the  construction  of  a  piece  of 
bridge-work. 

"  With  a  corundum  stone,  cut  off  the  remaining  portions 
of  the  crowns  level  with  the  gum  margins.  Prepare  the  roots 
in  any  of  the  well-known  ways,  thoroughly  cleansing  the  apical 
portions  and  filling  them  with  whatever  material  is  desired, 
being  careful  only  that  the  work  is  well  done.  For  the  better 
retention  of  the  filling  material  to  be  placed  in  the  pulp-chamber, 
retaining-grooves  can  be  made  or  retaining-posts  inserted. 
Take  a  piece  of  binding-wire  (No.  26,  American  gauge),  say 
2^  inches  long,  pass  it  around  the  neck  of  the  molar  stump, 
cross  the  free  ends,  and,  holding  the  wire  in  place  with  one  finger, 
twist  the  ends  with  a  pair  of  flat-nosed  pliers  until  the  wire  clasps 
the  tooth  closely  at  every  point  (Fig.  459).  When  there  are  any 
irregularities  in  the  contour  of  the  tooth,  it  is  necessary  to  press 
the  wire  into  them  with  an  approximal  burnisher.  It  is  obvious 
that  the  ring  thus  formed  will  show  the  exact  size  and  shape  of 
the  neck  of  the  tooth.  Remove  the  ring  carefully,  lay  it  on  the 
lead  anvil,  put  over  it  a  piece  of  flat  metal,  and  with  a  smart  blow 
from  a  hammer  drive  the  wire  into  the  lead  (Fig.  460).  Upon 
removing  the  wire  an  exact  impression  of  the  ring  will  be  left  in 
the  lead  anvil.  (This  part  of  the  work,  as  indeed  all  others, 
should  be  done  carefully  as  described.  The  wire  ring  may  be 
driven  into  the  lead  by  a  direct  blow  of  the  hammer  face,  but 
the  blow  might  not  strike  equally,  and  the  interposition  of  the 
flat  metal  held  level  insures  an  even  impression.  A  piece  of  an 
old  file  is  best,  as  the  file-cuts  keep  the  wire  from  slipping.) 

"  Next,  cut  the  wire  ring  at  the  lap,  straighten  out  the  wire, 
and  select  a  suitable  collar  by  comparing  the  length  of  the  wire 
with  the  straight  lines  in  the  diagram,  which  show  the  inside 
diameters  of  the  various  sizes.  Should  none  of  these  corres- 
pond exactly,  take  preferably  the  next  size  smaller.  It  will  be 
remembered  that  the  collars  are  No.  30  in  thickness,  while  the 
wire  with  which  the  conformation  is  secured  is  No.  26.  This  dif- 
ference permits  the  collar  when  contoured'  to  shape  to  enter  the 
lead  impression  readily,  a  decided  advantage  in  fitting.  Having 
selected  the  collar,  fit  it  to  mandrel  No.  5,  with  the  peen  of  the 
hammer,  holding  it  upon  the  lead  anvil,  and  using  a  slight  push- 


376 


MECHANICAL    DENTISTRY. 


ing  force  to  help  in  stretching  and  forming  it  (Fig.  461).  Hav- 
ing driv^en  the  collar  to  form,  remove  it  from  the  mandrel  and 
try  in  the  lead  impression.  If  it  does  not  fit  exactly  return  it  to 
the  mandrel  and  stretch  it  a  little,  when  it  will  usually  fit  perfectly, 
as  the  mandrels  have  been  designed  carefully  to  the  average 
shapes  which  obtain  in  the  great  majority  of  tooth-necks.  In 
the  exceptional  cases  where  the  collar  does  not  fit,  it  can  be 
readily  contoured  to  the  exact  shape  with  a  pair  of  flat-nosed 
pliers.     Of  course,  if  it  fits  the  impression  in  the  lead,  it  will  fit 


Fig.  459. 


Fig.  461. 


Fig.  460. 


the  neck  of  the  tooth,  always  provided  the  measurement  and  the 
impression  have  been  carefully  made. 

"  If  the  collar  or  band  has  been  accidentally  stretched  too 
much,  or  if,  for  any  reason,  when  brought  to  shape,  it  is  too 
large,  its  root  end  can  easily  be  reduced  to  the  proper  size  by  the 
use  of  the  contractor.  Place  the  edge  of  the  collar  which  is  to 
fit  in  the  root  in  the  proper  hole ;  hold  it  level  with  a  piece  of  file 
as  in  taking  the  lead  impression  of  the  ring,  and  tapping  lightly 
on  the  file  drive  the  collar  into  the  plate  (Fig.  455)  until  the  pro- 
per reduction  is  made.  The  collar  is  next  '  festooned  '  to  corre- 
spond to  the  shape  of  the  maxillary  ridge.  Lay  it,  gum  edge 
up,  on  the  lead  anvil,  and  with  the  piece  of  flat  file  and  the 
hammer  drive  it  into  the  lead.     A  few  cuts  with  a  fine  half-round 


BRIDGE-DENTURES. 


377 


file  across  the  approximal  diameter  will  conform  the  edges  to 
the  surface  of  the  ridge  (Fig.  462).  Then  place  the  collar  in 
position,  and,  having  ascertained  just  how  far  it  should  go  down 
on  the  root,  remove  it,  and  with  the  small  spring  punch  in  the 
collar  pliers  (Fig.  457)  form  projections  on  the  inside  of  the  band 
at  the  proper  points  to  serve  as  stops  which,  resting  on  the  top 
of  the  root,  will  prevent  the  collar  from  being  forced  further 
down  upon  it  than  is  desirable  (Fig.  463). 


Fig.  462. 


Fig,  464. 


Fig.  463. 


"  A  collar  for  the  cuspid  is  then  fitted  in  the  same  manner, 
using  mandrel  No.  6  for  shaping,  after  which  the  case  is  ready 
for  the  building  of  the  bridge. 

"  Place  both  collars  in  position  and  take  an  impression  of  the 
parts,  including  the  interiors  of  the  excavated  pulp-chambers, 
from  which  make  a  cast  in  the  usual  way.  Bend  a  short  piece 
of  half-round  gold  or  platinum  wire  into  the  form  of  a  horse- 
shoe, the  two  extremities  of  which  shall  fit  into  the  roots  of  the 
molar.  Then  take  a  longer  piece  of  the  same  wire,  somewhat 
more  than  enough  to  extend  from  the  toe  of  the  horseshoe  when 


378  MECHANICAL    DENTISTRY. 

in  position  to  the  cuspid  root ;  bend  one  end  of  it  at  a  right 
angle,  or  nearly  so,  to  fit  the  root  of  the  cuspid,  and  (cutting  off 
any  excess  of  length)  solder  the  other  end  to  the  toe  of  the 
horseshoe.  The  bar  extending  between  the  two  roots  is  the 
truss  of  the  bridge.  Next,  place  the  appliance  on  the  cast  (Fig. 
464),  holding  it  in  position  with  wax,  and  select  the  teeth  to  take 
the  place  of  the  missing  bicuspids  and  molar.  The  best  form 
for  this  purpose  is  a  tooth  having  holes  extending  through  it 
vertically  from  the  neck  to  the  grinding  surface,  similar  to  the 
well-known  Bonwill  Crown. 

"  The  crowns  used  should  be  large  enough  to  fill  the  space 
rather  tightly,  even  if  their  sides  have  to  be  flattened  to  let 
them  in.  If  the  teeth  do  not  fill  the  space  perfectly,  a  small 
portion  of  plastic  filling  material  crowded  between  them,  as  mor- 
tar between  the  granite  blocks  in  the  arch  of  a  railway  bridge, 
will  greatly  increase  the  strength  of  the  work. 

"  After  the  teeth  are  ground  to  fit  and  the  proper  length  for 
occlusion  ascertained,  the  truss  is  covered  with  a  film  of  wax, 
upon  which  the  crowns  are  again  pressed  to  their  positions. 
Upon  the  removal  of  the  crowns  the  impression  of  the  holes 
running  through  them  will  be  found  in  the  wax.  At  these 
points  drill  holes  through  the  bar  with  a  small  twist-drill  run  by 
the  dental  engine,  and  into  these  fit  and  solder  the  pins  for  the 
support  of  the  crowns,  as  shown  in  Fig.  465. 

"  The  bridge  is  now  ready  to  be  attached  permanently.  Set 
the  crowns  in  position  upon  their  supporting  pins,  to  secure  the 
proper  alignment.  (If  the  operation  were  upon  the  upper  jaw 
they  would  have  to  be  held  with  wax.)  Put  into  the  canals  of 
the  supporting  roots  (the  cuspid  and  first  molar)  a  sufficient 
quantity  of  some  quick-setting  plastic,  as  oxyphosphate,  to 
•about  half-fill  the  pulp-chamber,  but  not  enough  to  prevent  the 
supports  of  the  truss  from  being  forced  home.  Force  the 
bridge  supports  to  place,  and  after  allowing  the  filling  material 
to  become  set  remove  the  crowns.  Fill  the  remainder  of  the 
pulp-chamber  and  the  whole  of  the  collar  with  gold,  amal- 
gam, gutta-percha,  oxyphosphate,  or  other  suitable  plastic 
(Fig.  465).  Set  the  crowns  permanently,  the  molar  and  cuspid 
first,  as  this  affords  greater  facility  for  the  trimming  off  of  any 


BRIDGE-DENTURES. 


579 


excess  of  the  filling  material  used  in  the  attachment.  For 
attachment  of  the  crowns,  gutta-percha  is  probably  the  best 
material,  as  crowns  set  with  it  are  readily  removed  for  the  cor- 
rection of  any  inaccuracies  of  occlusion  or  alignment,  by  grasping 
them  between  the  beaks,  previously  w^armed,  of  a  pair  of  uni- 
versal lower  m.olar  forceps.  The  heat  warms  the  gutta-percha 
and  releases  the  tooth,  which  can  then  be  reset  properly.  In 
attaching  crowns  with  gutta-percha  the  holes  in  the  crowns  are 
first  filled  with  the  material,  after  which  the  crown  is  warmed 
and  forced  to  place.  Any  of  the  other  plastics  ordinarily  used 
in  setting  Bonwill  crowns  can  be  employed,  at  the  discretion  of 
the  operator.     Fig.  466  shows  the  case  completed. 

Fig.  466. 


"  In  securing  the  occlusion  of  a  piece  of  bridge-work  it  is 
well  to  make  the  artificial  teeth  a  little  short,  so  that  the  natural 
teeth  on  both  sides  will  meet  the  first  shock  of  mastication. 
Nature  will  correct  the  occlusion  in  time  by  slightly  elongating 
the  roots  supporting  the  bridge.  If  the  artificial  crowns  are 
permitted  to  strike  the  natural  teeth  from  the  first,  the  undue 
strain  upon  the  two  supporting  roots  will  cause  soreness  and, 
perhaps,  more  serious  consequences. 

"  When  a  sound  tooth  is  to  be  used  as  one  of  the  supports  of 
the  bridge,  a  modification  of  the  method  just  described  is  neces- 
sary. Take  a  case  where  it  is  desired  to  bridge  the  space  caused 
by  the  loss  of  the  right  inferior  bicuspids  and  first  molar.  The 
crown  of  the  right  cuspid  is  nearly  gone,  but  the  root  is  sound 
and  capable  of  supporting  one  end  of  the  bridge.  The  other 
end  will   be  attached  to  the   second  molar,  which   is  a   sound 


380 


MECHANICAL    DENTISTRY. 


tooth.  Prepare  and  band  the  cuspid  root  as  before,  dress  off 
the  second  molar  crown  until  it  is  slightly  smaller  than  the  neck, 
so  as  to  permit  a  cap  to  be  telescoped  over  it,  and  take  the 
measure  of  the  crown  with  the  binding  wire.  Select  a  suitable 
seamless  collar  of  sufficient  width  to  extend  from  the  neck  to  a 
little  beyond  the  grinding  surface  and  drive  it  up  on  the  proper 
mandrel  to  get  the  general  shape,  but  not  the  full  size  required 
to  fit  the  tooth,  leaving  it  so  that  the  edge  having  the  larger 
circumference  will  just  pass  over  the  end  of  the  crown  ;  place  the 
collar  on  the  tooth  and  with  a  block  of  wood  and  the  mallet  tap 
it  to  place  just  beyond  the  free  margin  of  the  gum.  This  method 
will  make  a  close  fit,  as  the  collar  will  readily  stretch  all  that  is 
necessary.     With  a  sharp-pointed  instrument  mark  the  length  of 

Fig.  467. 


the  crown,  remove  the  collar,  and  cut  it  to  the  proper  width  as  in- 
dicated. Then  in  a  piece  of  gold  plate  of  the  thickness  used  for 
caps  form  four  little  depressions  of  the  general  character  of  an 
impression  of  the  molar  cusps.  An  easy  way  to  do  this  is  to  lay 
the  plate  on  the  lead  anvil ;  then  with  the  ball  on  the  end  of  an 
ordinary  socket-handle  and  the  hammer  the  depressions  are  made 
in  a  moment.  Set  the  collar  on  the  plate,  borax  it,  charge  with 
solder,  and  heat  till  the  solder  flows.  Cut  off  the  surplus  plate 
and  a  perfect  cap  for  the  molar  is  made.  Place  it  on  the  tooth  and 
take  an  impression,  and  thereafter  proceed  as  before  directed  to 
make  the  truss  of  the  bridge  and  mount  the  teeth,  except  that  in 
this  case  the  posterior  end  of  the  truss  is  to  be  soldered  to  the 
molar  cap.  For  the  final  attachment  place  a  little  oxyphosphate 
or  other  plastic  filling  material  in  the  cap  to  secure  it  firmly  (Fig. 
467),  first  cutting  a  slot  in  the  crown  end  for  the  escape  of  the 


BRIDGE-DENTURES. 


381 


excess  of  material.  Pressure  upon  the  filling  material  hastens 
its  hardening. 

"Detachable  Bridge-work. — A  description  of  two  or  three 
methods  of  constructing  detachable  bridges  by  the  mandrel 
system,  will  suffice  to  indicate  the  general  principles  involved. 
Having  these,  each  operator  will  find  it  an  easy  task  to  devise 
the  modifications  necessary  to  adapt  a  method  to  individual 
cases. 

"  The  first  method  is  especially  applicable  to  cases  where  both 
ends  of  the  bridge  are  attached  to  roots,  as,  for  example,  the 
inferior  cuspid  and  second  molar  roots  of  the  left  side,  the  inter- 
vening teeth  having  been  lost.  The  operation  is  conducted  as 
described  in  the  first  case  of  fixed  bridge-work  down  to  the  con- 
struction of  the  truss,  for  which  in  this  method  square  gold  wire 
is  used.  Having  cut  the  wire  of  the  proper  length,  lay  it  upon 
a  piece  of  gold  plate  (about  No.  26,  American  gauge)  of  the 
same  length  and  full  three  times  as  wide,  and,  placing  the  two 
upon  the  lead  anvil,  with  a  hammer  and  the  piece  of  file  before 
used  drive  them  into  the  lead.  This  will  form  the  plate  into 
what  we  may  call  an  open  trunk  which  fits  the  square  wire. 
Remove  the  two  from  the  lead  together  and,  without  separat- 
ing them,    curve    to    the 

proper  shape  to  form  the  ^'°-  46^- 

truss.  Grind  crowns  havT 
ing  vertical  holes,  like 
the  Bonwill,  to  fit,  and 
having  determined  the 
proper  points  for  the  sup- 
porting pins,  drill  through 
both  trunk  and  bar  at 
these  points.  Separate  the 
bar  from  the  trunk,  and 
fit  and  solder  pins  to  the 
bar.       Construct    small 

tubes  to  fit  the  pins,  ream  out  the  holes  through  the  trunk  to 
admit  them,  and  set  the  tubes  with  solder  in  the  enlarged  holes 
(Fig.  468).  Fix  the  crowns  permanently  upon  the  tubes.  They 
may  be  mounted  in  any  of  the  approved  ways,  by  vulcanizing 


;82 


MECHANICAL    DENTISTRY, 


or  by  the  use  of  a  plastic  filling  material.  When  they  are  firmly 
set,  place  the  trunk  with  the  teeth  upon  the  bar  and  anchor 
it  permanently  as  already  described.  Fig.  469  shows  the  com- 
pleted work. 

"  In  this  method  the  truss  consists  of  the  bar  and  the  open 
trunk  which  covers  three  sides  of  it.  The  bar  is,  of  course, 
permanently  attached  to  the  roots  of  the  molar  and  cuspid,  but 
the  trunk  with  the  teeth  can  be  removed  at  any  time, 

"  The  second  method  of  constructing  a  detachable  bridge  is 

applicable  to  cases  where 
Fig.  469.  ,      ,       .    . 

one  or  both  01  the  sup- 
ports or  piers  are  sound 
teeth.  In  the  case  ad- 
duced for  illustration,  the 
right  inferior  cuspid  crown 
was  decayed,  and  both  of 
the  bicuspids  and  the  first 
molar  were  absent.  The 
supports  for  the  bridge 
were  the  sound  second 
molar  and  the  cuspid  root.  After  the  cuspid  root  was  prepared  and 
banded,  the  crown  of  the  molar  was  reduced  very  slightly,  not 
sufficient  to  destroy  the  enamel,  but  just  enough  to  permit  a 
collar  properly  fitted  to  pass  over  it.  A  collar  somewhat  wider 
than  the  length  of  the  crown  from  grinding  surface  to  neck 
was  fitted  and  cut  to  the  proper  width.  Two  lugs  were  then 
soldered  upon  the  anterior  and  posterior  sides  and  bent  to  fit 
into  the  approximal  fissures,  which  were  slightly  cut  out  to 
admit  them.  An  impression  was  taken,  the  collar  coming  away 
in  the  plaster,  and  a  cast  was  made  with  the  collar  in  position. 
A  coned  tube  was  then  made  for  the  root  of  the  cuspid  and  a 
coned  pin  fitted  into  it.  A  truss  of  half  round  wire  was  made 
to  which  the  collar,  coned  pin  and  the  molar  were  next  soldered 
(Fig.  470).  A  half-clasp  to  grasp  the  lateral  was  next  soldered 
to  the  end  of  the  truss,  to  be  supported  by  the  cuspid.  The 
object  of  this  clasp  was  to  guard  against  the  teeth  being 
thrown  out  of  proper  alignment  by  the  force  of  mastication. 
Bonwill  crowns  were  then  vulcanized  to  the  truss,  after  their 


BRIDGE-DENTURES. 


383 


supporting  pins  had  been  fitted  and  soldered  to  it.  (Counter- 
sunk crowns  can  be  used  as  well  in  the  same  way.  Plain  plate 
teeth  may  also  be  used  in  this  style  of  work,  in  which  event  they 
are  to  be  soldered  to  the  truss.)  The  bridge  was  then  ready  to 
be  set,  which  was  accomplished  in  the  following  manner :  The 
cuspid  root  was  nearly  filled  with  oxyphosphate,  and  the  coned 
tube  was  placed  upon  the  pin.  The  band  was  put  on  the  molar, 
and  the  coned  pin  with  the  tube  upon  it  was  forced  into  the 
plastic  in  the  cuspid  root.  As  soon  as  this  became  set,  the  tube 
was  held  permanently,  while  the  bridge  itself  could  be  removed 
whenever  desired  (Fig.  471). 

"  This  method  of  fixinsT  the  tube  allows  considerable  ranee  in 


Fig.  47c. 


Fig.  471. 


its  adjustment.  In  soldering  the  coned  pin  to  the  truss,  care 
should  be  taken  to  set  it  at  an  angle  exactly  parallel  to  the  axis 
of  the  molar ;  otherwise  there  will  be  difficulty  in  removing  the 
bridge. 

"  The  third  style  of  detachable  bridge-work  to  be  described 
involves  the  use  of  cusp  crowns  (Fig.  472)  for  supporting  posts 
or  piers.  Suppose  a  case  similar  to  that  described  at  page  382, 
where  a  bridge  is  required  to  extend  from  the  right  inferior  cus- 
pid to  the  right  inferior  second  molar,  with  only  the  roots  of  the 
two  teeth  named  as  supports.  Prepare  the  roots  and  pulp- 
chamber.  Set  screw-posts  into  the  dentine  for  anchorage  or  as 
retaining  pins,  and  fit  the  collars,  using  sizes  wide  enough  to 
form  the  walls  of  the  crowns.  Fill  the  pulp-chamber  and  about 
two-thirds   of   the   depth    of  the  collars   with  a    plastic    filling 


384  MECHANICAL    DENTISTRY. 

material,  packing  it  well  around  the  retaining  posts.  Select 
suitable  cusp  crowns  for  the  molar  and  cuspid  and  place  them 
in  the  ends  of  the  bands  to  ascertain  the  occlusion.  If  too  long, 
shorten  the  cusps  or  reduce  the  bands  with  engine  corundum- 
wheels  and  when  the  correct  articulation  is  found  form  a  small 
square  shoulder  in  the  lingual  edge  of  the  cuspid  and  in  the 
posterior  grinding  surface  of  the  molar.  Fill  the  remaining  por- 
tion of  the  collars  with  plastic  mixed  somewhat  thinner  than  the 
first  lot,  and  set  the  cusp  crowns  in  position.  If  there  are  antag- 
onizing teeth,  the  mere  closing  of  the  patient's  jaws  will  force  the 
crowns  to  place.  If  there  are  no  antagonizing  teeth  the  crowns 
can  be  readily  tapped  to  place  with  the  mallet,  using  a  piece  of 
wood  as  a  driver.     Allow  the  filling  material  to  set  firmly,  trim- 

FiG.  472. 


ming  off  any  excess  which  may  exude  around  the  collars. 
Bridge  supports  or  piers  constructed  on  this  plan  are  strong  and 
durable,  and  likely  to  withstand  any  strain.  Take  an  impression, 
and  proceed  to  fit  seamless  collars  to  telescope  over  those  already 
set  upon  the  cuspid  and  second  molar  roots.  It  will  be  remem- 
bered that  these  collars  are  so  made  that  each  size  telescopes 
into  the  next  higher  series.  If  the  proper  sizes  are  selected  for 
the  outside  bands,  the  work  of  fitting  is  readily  and  quickly 
accomplished,  forming  tubes  which  slide  easily  over  the 
supporting  piers,  and  at  the  same  time  fit  closely.  It  is  only 
necessary  to  take  care  in  shaping  the  tubes  not  to  drive  them 
too  far  up  on  the  mandrels,  and  thus  stretch  them  so  as  to 
destroy  the  fit.  To  the  outer  end  of  each  of  the  tubes  solder  a 
small  piece  of  gold  plate,  forming  partial  caps  so  placed  as  to 
rest  when  in  position  upon  the  shoulders  previously  cut  in  the 
cusp  crowns.  Adjust  a  truss  bar  of  half-round  gold  wire,  to  the 
ends  of  which  solder  the  tubes   (Fig.  473).     The  truss  is  now 


BRIDGE-DENTURES. 


(85 


ready  for  the  teeth,  which  may  be  of  any  of  the  forms  used  for 
this  purpose,  and  they  may  be  attached  to  the  bar  in  any  way 
desired.     One  of  the  strongest  attachments  is  vulcanite, 

"An  easy  modification  of  the  plan  just  described  is  readily 
adapted  to  cases  where  only  a  small  space  is  to  be  filled  and  one 
end  of  the  bridge  is  to  be  supported  by  a  sound  tooth.  Thus, 
suppose  it  is  desired  to  bridge  a  space  formerly  occupied  by  the 
two  inferior  left  bicuspids,  the  crown  of  the  first  molar  being  a 
mere  shell.  The  operation  would  be  essentially  the  same  as  in 
the  previous  case,  except  that  the  sound  cuspid  would  be  util- 


FiG,  475. 


Fig.  474. 


ized  for  one  of  the  piers,  as  follows  :  Fit  a  seam.less  collar,  cut 
out  a  portion  of  it  so  that  it  will  embrace  only  about  two- thirds 
of  the  cuspid  crown,  and  solder  a  partial  cap  or  cover  to  it  (Fig. 
474),  Or,  the  cuspid  crown  may  be  separated  from  the  lateral 
incisor  with  a  diamond  disk  and  the  collar  allowed  to  embrace 
the  whole  crown. 

"  The  great  desideratum  in  constructing  a  piece  of  bridge- 
work  is,  of  course,  the  securing  of  perfect  usefulness  in  mastica- 
tion and  speech,  combined  with  absolute  comfort  and  cleanliness. 
The  closer  a  bridge  approaches  that  condition  where  its  wearer 
loses  consciousness  of  its  presence  in  his  mouth,  the  nearer 
perfection  it  is.  Scarcely  less  important,  however,  is  the 
necessity,'-  of  providing  for  repair.  Accidents  will  occur,  and  the 
25 


386  MECHANICAL    DENTISTRY, 

system  which  superadds  to  usefulness,  comfort,  and  beauty, 
ready  facility  for  repairing  breakages,  is  by  so  much  superior  to 
those  which  make  no  such  provision.  The  place  of  a  crown 
broken  from  a  bridge  constructed  by  any  of  the  methods  above 
described  can  be  easily  supplied,  and  the  piece  when  repaired 
will  be  as  strong  and  serviceable  as  it  was  originally." 

METHODS    OF    CONSTRUCTING    CROWNS    AND    BRIDGES    IN    CASE 
OF    IRREGULARITY. 

A  young  lady  of  about  twenty-two  years  called  upon  the 
writer  for  services.  Her  mouth  presented  a  very  homely 
appearance,  which  was  largely  due  to  the  ignorance  or  lack  of 
judgment  upon  the  part  of  her  dentist  in  former  years.  The 
history  of  her  case  can  be  given  in  a  few  words.  It  is  a  charac- 
teristic of  her  family  to  have  large,  strong  teeth,  with  the  cus- 
pids quite  prominent;  but  in  her  mouth  these  teeth  were  so 
prominent  as  to  disfigure  her,  and  when  she  commenced  to 
grow  into  womanhood,  her  mother  took  her  to  their  dentist  to 
have  the  irregularity  corrected.  This  gentleman,  as  I  have  said, 
through  bad  judgment  extracted  the  two  lateral  incisors,  and 
allowed  the  cuspids  to  come  down  and  forward  to  partially  take 
their  place.  Then  the  mischief  was  done.  The  mouth  was 
given  a  very  coarse  appearance  by  the  large  teeth  being  brought 
so  near  the  center,  and  as  they  did  not  entirely  fill  the  space,  an 
ugly  opening  was  left  between  these  teeth  and  the  central 
incisors.  (See  Fig.  475.)  When  the  lady  consulted  me,  it  was 
with  the  idea  of  having  the  cuspids  extracted,  and  two  smaller 
teeth  inserted  upon  either  side ;  it  was  her  wish  at  the  same 
time  to  have  it  done,  if  possible,  in  some  way  so  that  she  would 
not  have  to  wear  a  plate.  After  studying  her  case  it  was,  there- 
fore, decided  to  extract  those  teeth  which  should  have  been 
removed  in  the  first  place, — the  first  bicuspids.  Then  with 
suitable  regulating  appliances  the  angle  of  the  cuspids  was  cor- 
rected and  they  were  drawn  back  so  as  to  partially  fill  the  space 
formerly  occupied  by  the  first  bicuspids ;  at  the  same  time  the 
second  bicuspids  were  brought  into  line,  and  all  secured  with 
retaining  appliances,  which  were  worn  for  several  weeks.  A 
lateral  incisor  was  then  prepared  for  either  side,  and  inserted 


BRIDGE-DENTURES. 


387 


by  means  of  plate  and  pin  bridges.     Described   by   Professor 
Litch  on  page  302. 

Fig.  475- 


Fig.  476. 


The  result  obtained  u^as  exceedingly  gratifying,  a  fair  idea  of 
which  is  shown  in  Fig.  476. 

Fig.  477  represents  a  case  of  irregularity  treated  by  Dr.  Bon- 
will,  who  says  in  his  description  of  it — 

Fig.  477. 


"  This  shows   a  case  of  irregularity  which  was   beyond  cor- 
rection, on  account  of  the  poor  character  of  the  teeth,  their 


388  MECHANICAL    DENTISTRY. 

position  in  the  palatal  arch,  and  the  age  of  the  patient.  In  such 
cases  I  do  not  hesitate  to  cut  off  the  crown,  destroy  the  pulp, 
and  insert  an  artificial  crown.  The  crown  is  brought  in  the 
circle  and  connected  with  the  root  by  a  strip  of  heavy  gold 
plate.  The  plate  is  attached  to  the  root  with  a  post  or  a  screw 
with  a  nut." 

The  next  case  was  one  treated  by  Dr.  I.  N.  Broomell,  who 
gives  me  the  following  description  : — 

"  The  superior  cuspid  was  fully  a  quarter  of  an  inch  out 
of  line ;  standing  inside  the  arch  to  such  a  degree  that  a 
casual  glance  at  the  patient  would  lead  one  to  suppose  the  tooth 
was  missing.  It  was  also  imperfectly  developed,  so  that,  had 
age  and  other  circumstances  favored  its  restoration  to  the  proper 
position  in  the  arch,  its  malformation  made  it  inadvisable  to 
attempt  such  an  operation.  (Fig.  478.)  The  patient  being 
desirous  of  having  the  deformity  remedied,  at  least  so  far  as 
appearances  were  concerned,  I  proceeded  to  do  so  in  the  follow- 
ing manner:  Grinding  off  the  irregular  prominences  of  the 
tooth,  I  made  it  more  perfectly  conical  in  shape.  After  secur- 
ing an  impression  of  the  deformed  tooth  and  casting  zinc  dies, 
I  swaged  a  hollow  gold  cap  to  accurately  cover  the  whole  sur- 
face and  extend  slightly  under  the  gum.  This  added  thickness 
of  gold,  when  placed  over  the  tooth,  extended  the  labial  surface 
to  about  what  should  have  been  the  palatal  line  ;  thus  permitting 
me  to  adjust  by  grinding  and  filing  a  porcelain  tooth  with  its 
backing  to  the  cap.  These  were  soldered  together  and  the 
appliance  secured  on  the  cuspid  by  oxyphosphate  cement.  In 
this  case  no  pins  were  used,  the  cap  alone  being  sufficient  to 
hold  the  denture  in  position.  (A,  Fig.  478.)  It  has  now  been 
in  the  mouth  some  three  or  four  years,  during  which  time  I  have 
removed  it  several  times  in  order  to  be  satisfied  that  all  was  right 
under  the  cap.  In  fact,  I  consider  that,  when  it  is  at  all  possible 
to  do  so,  all  appliances  of  this  order,  including  small  pieces  of 
bridge-work,  should  be  so  constructed  that  they  maybe  removed 
from  time  to  time,  thus  affording  an  opportunity  to  detect  any 
carious  conditions, 

"  Another  case  which   I   will  briefly  present  was  somewhat 


BRIDGE-DENTURES. 


389 


similar  in  construction  to  the  one  just  described,  but  was  inserted 
under  different  circum- 
stances. For  some  rea-  ^  "^"  ^"^  ' 
son  unknown  to  the  pa- 
tient, he  had  lost  from  a 
lower  incisor  the  entire 
labial  surface,extending 
from  the  cutting  edge 
to  the  gum-margin,  and 
somewhat  below  it. 
The  lingual  half  of  the 
crown  remained,  and 
fortunately  the  pulp 
was  not  exposed.  (Fig. 
479.)  With  a  corun- 
dum wheel  I  ground  off  the  cutting  edge  of  the  tooth  (to 
the  horizontal  dotted  line  seen  in  Fig.  479)  until  it  was  below 
the  line  of  the  pins  in  the  porcelain  tooth,  which  had  been 
selected  because  its  cross  pins  were  near  its  cutting  edge,  and 
ground  the  porcelain  tooth  to  fit  the  inclined  surface  of  the 
natural  organ.  I  then  fitted  a  backing  of  very  thin  platinum, 
allowing  it  to  extend  over  the  whole  back  of  the  porcelain 
tooth,  including  the  inclined  surface.  After  making  a  cap  to 
perfectly  fit  the  lingual  surface  of  the  incisor,  I  pressed  it  around 
the  sides  until  I  could  solder  it  to  the  backing,  thus  making  a 
cap  (A,  Fig.  479)  which  completely  covered  the  abraded  tooth. 
Oxyphosphate  cement  being  used  in  setting  the  denture. 


CHAPTER  VI. 

PARTIAL  DENTURES  RETAINED  IN    THE    MOUTH 
BY  MEANS  OF  CLASPS. 

Remarks  on  the  Use  of  Clasps. — Clasps  or  metallic  bands 
have  been  long  and  very  generally  employed  as  a  means  of  re- 
taining parts  of  sets  of  teeth  in  the  mouth,  and  are  still  used,  to 
a  limited  extent,  for  that  purpose  by  many  practitioners.  When 
these  appliances  are  skilfully  adjusted,  and  all  the  conditions 
pertaining  to  the  mouth  and  remaining  natural  teeth  are  favor- 
able to  their  application,  they  afford  a  certain,  permanent,  and 
satisfactory  means  of  supporting  partial  dentures,  and  may  be 
employed,  under  such  circumstances,  with  comparative  safety  to 
the  natural  organs.  When  it  is  remembered,  however,  that  in 
a  lamentably  large  proportion  of  cases,  clasps  are  carelessly  or 
unskilfully  formed  and  fitted  to  the  teeth  ;  that  the  organs  of 
support  are  often  indiscriminately  selected,  and  are  neither 
adapted  in  form,  situation,  or  structure  for  such  uses  ;  and  that 
they  are  frequently  diseased  and  insecurely  attached  to  the  jaw, 
or  are  mutilated  for  the  reception  of  clasps,  we  can  readily  un- 
derstand to  what  unlimited  extent  this  method  is  subject  to 
abuses.  In  fact,  (ew  other  special  processes  in  mechanical  prac- 
tice have  been  so  fruitful  of  evil  as  that  under  consideration,  and 
the  opprobrium  which  but  too  justly  attaches  to  it  in  profes- 
sional as  well  as  popular  estimation,  is  chargeable  more  properly 
to  bad  faith  and  unskilfidncss  on  the  part  of  the  operator,  and  to 
zvant  of  necessary  attention  to  the  cleanliness  of  the  substitute  and 
the  organs  of  the  mouth  on  the  part  of  the  patient,  than  to  any  in- 
herent unsuitableness  of  the  method  itself.  Nevertheless,  it 
must  be  admitted  that,  under  the  most  favorable  circumstances, 
the  teeth  clasped  are  not  wholly  exempt  from  liability  to  injury, 
and  this  circumstance  in  itself  renders  it  the  more  imperative 
that  the  process  should  be  surrounded  by  all  the  safeguards  that 
skill  and  ingenuity  can  devise. 

390 


PARTIAL    DENTURES    RETAINED    BY    CLASPS.  39 1 

The  opinion,  at  one  time  current,  that  the  injury  inflicted  upon 
the  teeth  by  clasps  was  mainly  the  result  of  mechanical  action, 
has  given  place  to  the  more  defensible  view  that  the  causes  con- 
cerned in  its  production  are  chiefly  of  chemical  origin.  Thus, 
the  secretions  of  the  mouth,  with  particles  of  alimentary  and 
other  substances,  being  retained  between  the  clasp  and  the  tooth 
for  a  sufficient  period  of  time,  and  exposed  to  the  favoring  con- 
ditions of  warmth  and  immobility,  suffer  a  process  of  putrefactive 
decomposition  by  which  acids  are  eliminated,  and  which,  in  their 
nascent  state,  act  with  perceptible  energy  upon  the  bone  consti- 
tuents of  the  tooth,  producing  disintegration  and  ultimate  decay. 
The  rapidity  and  extent  of  this  action  will  depend  much  upon 
the  nature  and  quantity  of  the  acids  present;  the  structural  char- 
acteristics and  vital  resistance  of  the  teeth  ;  the  mechanical  exe- 
cution, adaptation,  and  composition  of  the  plate  ;  and  the  personal 
habits  of  the  patient  with  respect  to  cleanliness. 

The  most  usual  seat  of  structural  disorganization  in  these  cases 
is  at  the  neck  of  the  tooth,  where  the  enamel  is  thinnest,  and  is 
sometimes  limited  to  a  circumscribed  spot,  but  oftener  extends 
on  a  line  with  the  gum,  involving  nearly  or  quite  all  of  that  part 
of  the  neck  of  the  .tooth  embraced  by  the  clasp.  At  first  the 
enamel  becomes  bleached  and  softened  as  though  macerated,  and 
is  ordinarily  very  sensitive  to  both  chemical  and  mechanical 
irritants.  With  a  continuance  of  the  cause,  the  superficial  por- 
tions of  the  affected  parts  become  more  and  more  thoroughly 
disintegrated,  and  sooner  or  later  assume  the  open  form  and 
characteristics  of  ordinary  decay.  If,  as  was  formerly  supposed, 
decay  or  solution  of  tooth-bone  in  these  cases  resulted  from 
mechanical  attrition,  or  wearing  away  of  the  enamel,  the  injury 
would  be  inflicted  at  points  distant  from  the  neck  of  the  tooth 
where  the  clasp  lies  in  more  direct  and  immediate  contact  with 
the  protuberant  portions  of  the  crown  ;  but  we  find  that  decay, 
from  this  cause,  is  not  only  of  infrequent  occurrence  at  such 
points,  but,  on  the  contrary,  the  enamel  here  is  frequently  found 
condensed  and  polished  by  the  mechanical  action  of  the  clasp. 
Certain  conditions  of  the  plate  and  clasp  undoubtedly  favor  me- 
chanical action  and  accelerate  the  destruction  of  the  tooth  ;  as 
where  the  clasp  bears  unequally  with  sharp  and  unfinished  edges 


392  MECHANICAL    DENTISTRY. 

upon  the  tooth,  or  where  the  base  is  faulty  in  its  adaptation  to 
the  mouth,  admitting,  by  its  mobility,  of  irregular  traction  or 
pressure  upon  the  organs  of  support.  Whenever  the  artificial 
appliance  is  thus  unskilfully  constructed  and  applied,  and  free 
interspaces  are  furnished  for  the  lodgment  and  retention  of 
particles  of  food,  and  the  teeth  clasped  are  defective  in  structure, 
and  we  have  conjoined  with  these  an  utter  disregard  of  cleanli- 
ness in  regard  to  the  substitute  and  remaining  natural  teeth,  the 
destruction  of  the  latter  is  certain,  rapid,  and  generally  irretriev- 
able. 

The  Teeth  to  which  it  is  most  Proper  to  Attach  Clasps. — 
The  utility,  comfort,  and  appearance  of  a  partial  set  of  artificial 
teeth  in  the  mouth  will  depend  much  upon  the  fitness  of  the 
natural  organs  selected  for  the  purpose  of  support.  "  A  clasp," 
says  Professor  Harris,  "  should  never  be  applied  to  a  loose  tooth, 
or  to  one  situated  in  a  diseased  socket,  or  which  is  so  much 
affected  by  caries  as  to  render  its  perfect  restoration  and  per- 
manent preservation  impracticable,  and  when  none  but  such  can 
be  had,  the  proper  course  to  pursue  is  to  extract  every  tooth  in 
the  jaw,  and  replace  the  loss  of  the  whole  with  an  entire  denture. 
The  application  of  clasps  to  diseased  or  loose  teeth,  always 
aggravates  the  morbid  condition  of  the  parts,  and  causes  the 
substitute  which  they  sustain  to  become  a  source  of  annoyance 
to  the  patient.  Besides,  such  teeth  can  be  retained  in  the  mouth 
only  for  a  short  time,  and  when  they  give  way,  the  artificial  appli- 
ance becomes  useless,  and  even  while  it  is  worn,  it  is  not  held 
firmly  in  place,  but  is  moved  up  and  down  by  the  action  of  the 
lips  and  tongue,  so  that  its  presence  can  hardly  escape  observa- 
tion from  the  most  careful  observer."  * 

Teeth,  also,  that  are  too  short  to  admit  of  sufficient  breadth  to 
the  clasp  to  impart  stability  to  the  substitute,  and  those  that 
stand  very  irregularly  in  the  arch,  rendering  it  difficult  for  the 
patient  to  apply  and  remove  the  appliance,  are  unsuitable  as 
organs  of  support. 

In  reference  to  the  individual  classes  of  teeth,  it  may  be  ob- 
served that  the  incisors,  both  as  regards  form  and  situation,  are 

*  "  Principles  and  Practice  of  Dental  Surgery,"  page  717. 


PARTIAL    DENTURES    RETAINED    BY    CLASPS.  393 

inadmissible  for  clasping,  and  are,  therefore,  never  used  for  this 
purpose.  The  cuspidati,  likewise,  being  placed  conspicuously  in 
the  front  part  of  the  mouth,  cannot  be  securely  embraced  with- 
out manifest  exposure  of  the  clasp ;  besides,  the  conical  form  of 
these  teeth  makes  the  use  of  a  very  slender  clasp  indispensable  ; 
hence,  these  teeth  are  rarely  employed,  and  may  only  be  used 
when,  in  the  judgment  of  the  operator,  the  necessities  of  the 
patient  for  the  time  being  seem  to  require  it. 

Either  the  anterior  or  the  second  molars,  when  sound  and 
firm,  offer,  in  respect  of  their  general  conformation  and  position 
in  the  arch,  the  most  desirable  and  efficient  support  for  parts  of 
sets  of  teeth.  The  crowns  of  these  teeth  generally  afford  ample 
breadth  to  the  clasp  ;  have  nearly  parallel  walls;  and  furnish, 
by  the  strength  and  im.mobility  of  their  attachments  to  the  jaw, 
the  greatest  security  to  the  artificial  appliance.  The  anterior 
molars  are  preferable  where  these  are  remaining  in  good  condi- 
tion, or  are  susceptible  of  being  properly  restored  and  preserved 
if  diseased  or  carious. 

Of  the  bicuspids,  the  posterior  are  to  be  selected,  if  practica- 
ble, as  these  better  favor  the  concealment  of  the  clasps  ;  to  effect 
which  more  perfectly,  in  the  use  of  either  the  first  or  second 
bicuspids,  it  will  be  sufficient  in  many  cases  to  embrace  only 
the  posterior  half  of  the  crown. 

The  third  molars,  or  wisdom  teeth,  will  seldom  admit  of  the 
application  of  clasps,  as  the  crowns  of  these  teeth  are  usually 
very  short  and  cone-shaped,  the  walls  converging  abruptly  from 
the  gum  ;  besides,  the  retractive  forces  applied  to  the  anterior 
teeth  of  the  substitute  would,  on  account  of  the  increased  lever- 
age consequent  upon  the  extension  of  the  plate  back  to  these 
teeth,  tend  either  to  disengage  the  clasps  or  produce  displace- 
ment of  the  teeth  to  which  they  are  applied. 

In  Supplying  the  Loss  of  the  Inferior  Incisors,  the  appli- 
ance should,  as  a  general  thifig,  be  attached  either  to  the  anterior 
or  posterior  bicuspids,  as  these  teeth  stand  more  nearly  vertical 
in  the  arch.  In  fixing  partial  lower  dentures,  it  will  be  sufficient 
to  simply  provide  against  mobility  of  the  base,  as  they  are 
favored  rather  than  opposed,  as  above,  by  gravitation. 

The  Replacement  of  the  Inferior  Teeth  posterior  to    one 


394  MECHANICAL    DENTISTRY. 

or  both  bicuspids,  however,  is  more  frequently  demanded  ;  in 
which  case  it  is  customary  to  attach  the  clasps  to  the  teeth  im- 
mediately in  front  of  and  adjoining  the  vacuities  on  each  side. 
It  will  not,  however,  be  necessary  to  attach  clasps  in  these  cases 
whenever  the  edentulous  portions  of  the  jaw  present  a  distinctly 
scooped  form  or  marked  concavity  of  outline,  forming  a  kind  of 
bed  for  the  plate.  If,  on  the  other  hand,  the  ridge  falls  back 
with  a  tolerably  uniform  inclination  from  the  teeth  in  front,  with 
no  sufficient  elevation  at  the  base  of  the  coronoid  process,  it 
may  become  necessary  to  provide  against  backward  displace- 
ment of  the  substitute  by  attaching  clasps,  as  before  stated,  to 
the  teeth  immediately  in  front.  In  any  case,  if  the  third  molars 
remain,  partial  or  stay  clasps  may  be  attached  to  each  heel 
of  the  plate,  and  so  adjusted  as  to  rest  against  the  anterior  face 
of  these  teeth,  obviating  entirely  the  necessity  of  clasps  in 
front. 

Separation  of  the  Teeth  for  the  Reception  of  Clasps. — 
The  practice  of  separating  the  teeth  with  the  file  to  provide  for 
the  application  of  clasps  should  always  be  avoided  if  practicable, 
since  the  liability  of  the  teeth  thus  denuded  of  enamel  to  decay 
is  greatly  increased  under  circumstances  so  favorable  to  their 
disintegration.  In  the  case  of  young  subjects,  especially,  where 
the  teeth  are  but  imperfectly  consolidated,  and  in  adults  whose 
teeth  are  defectively  organized,  presenting  but  a  feeble  resistance 
to  the  disintegrating  agents  usually  present  in  the  mouth,  the 
use  of  the  file,  for  the  purpose  indicated,  is  eminently  pernicious, 
and  should  never  be  resorted  to.  When  it  is  found  necessary  to 
separate  the  teeth  for  the  reception  of  clasps,  a  thin  diamond 
disk  should  be  employed,  as  it  is  less  annoying  to  the  patient, 
does  the  work  in  less  time,  and  is  not  so  destructive  to  the 
tooth  structure  as  the  file. 

Whenever  a  plain  necessity  for  this  operation  exists,  a  careful 
examination  of  all  the  teeth  to  which  it  is  proper  to  apply 
clasps  should  be  made,  and  if  decay  is  found  upon  their  proxi- 
mate surfaces,  the  separation  should  be  made  between  the  teeth 
so  affected;  and  this  circumstance  should,  in  most  cases,  deter- 
mine the  selection,  though  the  affected  tooth  or  the  one 
adjoining    may   not    be    esteemed,   in   other   respects,  the    best 


PARTIAL    DENTURES    RETAINED    BY    CLASPS.  395 

for  the  purposes  of  support.  If  decay  exists  on  the  proximate 
surface  of  only  one  of  the  teeth  to  be  separated,  a  safe-sided 
diamond  disk,  revolved  by  the  dental  engine,  should  be 
employed,  and  the  cutting  confined  entirely  to  the  carious 
tooth,  leaving  the  enamel  of  the  one  adjoining  unbroken.  The 
cavity  of  decay  should  be  well  filled,  and  the  filed  surface 
thoroughly  condensed  and  polished. 

Modifications  in  the  Form  of  Clasps. —  i.  Plain  Band.    The 
most  usual  form  of  clasp  is  that  shown  in  Fig.  480.     It  consists 
of    a    plain    metallic    band    of 
greater  or  less  width  and  thick-  ^^^'  ^ 

ness,  and  is  made  to  embrace 
the  larger  portion  of  the  circum- 
ference of  the  tooth.  In  regard 
to  the  general  properties  of 
metallic  clasps,  it  may  be  said 
that    they  should  be,  as  nearly 

as  practicable,  of  the  same  quality  or  fineness  as  the  plate  or 
base  to  which  they  are  united ;  they  should  be  heavy  enough 
to  impart  adequate  security  to  the  attachment,  say  twice  the 
thickness  of  the  base,  and  exceeding  this  in  some  cases ;  and 
sufficiently  elastic  to  embrace  accurately  the  more  contracted 
parts  of  the  teeth  after  having  been  temporarily  forced  apart  in 
passing  over  the  enlarged  portions  of  the  crowns.  In  con- 
structing a  plain  band  or  clasp,  a  strip  of  sheet  lead  or  other  pli- 
able substance  may  first  be  fitted  accurately  to  the  plaster  tooth, 
making  it  of  the  required  width,  and  shaping  the  edge  next  the 
gum  in  conformity  with  the  irregularities  in  the  latter  around 
the  neck  of  the  tooth  ;  the  exact  counterpart  of  the  pattern  thus 
obtained  is  then  cut  from  the  plate  to  be  used  in  the  formation 
of  the  clasp.  The  strip  thus  obtained  is  then  bent  with  round- 
nosed  or  grooved  pliers  (Fig.  481),  until  conformed  as  perfectly 
as  possible  to  every  portion  of  the  surface  of  the  tooth  em- 
braced by  it.  This  coaptation  should  be  sufficiently  accurate  to 
exclude  perfectly  all  solid  substances  from  between  the  clasp 
and  the  tooth.  A  more  accurate  adaptation  of  the  clasp  may 
be  secured  in  the  following  manner :    First  secure  a  pattern,  as 


39^ 


MECHANICAL    DENTISTRY. 


before  described,  and  by  this  cut  from  a  thin  strip  of  platinum^, 
say  No.  30  or  32  of  the  gauge-plate,  a  band  of  the  required  size 
and  form,  and  press  or  burnish  it  accurately  to  the  form  of  the 
plaster  tooth.  The  soft  and  pliant  condition  of  this  metal  will 
admit  of  its  being  easily  adapted  to  any  irregularities  upon  the 
lateral  walls  of  the  tooth.  The  band  thus  molded  to  the  tooth 
is  then  carefully  removed  from  the  model,  or  the  mouth,  if  fitted 
to  the  tooth  in  the  latter,  and  its  central  portion  filled  with  a 
mixture  of  plaster  and  sand,  with  a'  small  metallic  wire  or  bar 
passing  through  the  center  to  support  it  while  soldering.  The 
outer  or  exposed  surface  is  then  coated  with  a  mixture  of 
borax,  and  small  scraps  or  fragments  of  gold  plate  of  equal 
fineness  with  the  main  plate  are  placed  at  intervals  and  fused 
with   the    blowpipe   until    diffused   uniformly   over  the  surface. 

Fig.  481. 


Small  pieces  may  be  added  from  time  to  time,  until  the  required 
thickness  of  the  clasp  is  obtained.  The  piece  should  be  heated 
uniformly  throughout  to  induce  an  even  flow  of  the  gold  over 
the  exterior  surface  of  the  platinum  ring.  By  this  method  a 
faultless  adaptation  of  the  clasp  to  the  tooth  may  be  secured, 
provided  the  form  of  the  latter  is  correctly  represented  on  the 
model.  In  all  cases  where  the  plain  band  is  used,  it  should  be 
made  as  broad  as  the  tooth  will  admit  of,  as  a  clasp  so  formed 
gives  greater  stability  to  the  plate,  and  does  not  endanger  the 
tooth  clasped  in  any  greater  degree  than  a  narrow  one. 

2.  Standard  Clasp. — To  guard  more  perfectly  against  the 
retention  of  vitiated  secretions  and  particles  of  food  around  the 
neck  of  the  tooth,  a  method  of  constructing  clasps  has  been 
devised  and  introduced  to  the  notice  of  the  profession  by  Dr. 
C.  W.  Spalding,  which,  by  leaving  the  cervical  portion  of  the 


PARTIAL    DENTURES    RETAINED    BY    CLASPS.  397 

tooth  in  a  great  degree  uncovered,  permits  the  action  of  the 
tongue  and  the  natural  circulation  of  the  fluids  of  the  mouth  to 
wash  or  cleanse  that  portion  of  the  tooth  most  liable  to  be 
injuriously  affected.  In  commenting  on  this  method,  Dr.  S. 
remarks :  "  The  writer  has  for  many  years  been  in  the  habit  of 
employing  Jim-roiv  clasps  for  the  purposes  of  support,  making 
them  of  sufficient  thickness  to  give  the  required  strength,  and 
attaching  them  to  the  plate  by  means  of  standards,  so  arranged 
as  to  induce  the  removal  of  accumulations  between  the  clasp  and 
tooth,  by  the  circulation  of  the  saliva  (Fig.  482).  The  use  of 
one  or  more  standards  as  a  means  of  attachment  also  provides, 
by  a  variation  of  their  length,  for  the  grasping  of  the  tooth  at 
any  desired  point.  If  the  tooth  is  long,  and  particularly  if  it  is 
at  the  same  time  bell-crowned,  the  point  selected  should  be 
toward  the  grinding  surface,  as  far  from  the  gum  as  is  found 
practicable.  If  the  tooth  is  short  and  of  such  form  that  it  can 
be  successfully  clasped  at  no  other  point  than  that  near  the 
gum,  the  plate  should  be  cut  away  at  least  one  or  one  and  a  half 
lines  from  the  tooth,  and  standards  introduced  for  the  purpose 
of  promoting  circulation,  by  affording  a  free  passage  for  the 
ingress  and  egress  of  fluids.  These  standards  should  also  be 
narrow,  no  wider  than  the  clasp  itself,  and  should  constitute  the 
only  point  of  union  between  the  clasp  and  plate.  Half-round 
wire  will  be  found  to  be  a  very  convenient  article  for  making 
clasps.  The  particular /"<?/';«  of  the  clasp  is,  however,  immaterial 
if  it  is  both  narrow  and  strong."  * 

3.  Scalloped  Clasp. — Somewhat  analogous  in  form  to  the 
clasp  just  described,  and  constructed  with  a  similar  design,  is 
the  one  recommended  by  Dr.  B.  T.  Whitney.  A  plain  band  of 
gold  is  fitted  to  the  tooth  in  the  manner  first  described,  when 
that  portion  of  it  next  the  gum  on  the  lingual  side  of  the 
tooth  is  scalloped  or  cut  away  in  the  form  of  a  semicircle  or 
arch,  the  ends  of  the  clasp  being  in  like  manner  narrowed  suffi- 
ciently to  relieve  them  from  contact  with  the  neck  of  the  tooth. 
The  intermediate  points  of  the  clasp  which  serve  to  unite  the 
latter  to  the  base  may  be  two  or  more  in  number,  and  should 

*  American  Dental  Review,  vol.  1,  p.  12. 


398 


MECHANICAL    DENTISTRY. 


be  wide  enough  to  impart  adequate  strength  to  the  attachment. 
A  clasp  so  formed  and  appHed  to  the  base  will  present  very 
nearly  the  appearance  of  the  standard  clasp  as  represented  in 
Fig.  482.  Dr.  W.  recommends  soldering  but  a  single  point  at 
first,  and  then  having  tried  the  plate  in  the  mouth  and  adjusted 
the  clasp  properly  to  the  tooth,  remove  and  solder  the  remain- 
ing point  or  points. 

4.  Partial  or  Stay  Clasp. — This  form  of  clasp,  instead  of  em- 
bracing the  tooth,  is  designed  to  steady  or  fix  the  substitute  in 
place  by  simply  resting  against  one  side  of  the  tooth  to  which 
it  is  applied.  They  should  be  so  connected  to  the  plate  that, 
when  pressed  over  the  enlarged  portions  of  the  crowns  of 
the  teeth,  they  will  spring  readily  into  place  and  adapt  them- 


FiG.  482. 


selves  closely  to  the  more  contracted  parts  near  the  gum.  In 
cases  where  there  is  no  adequate  opposing  force  to  that  exerted 
by  the  clasp,  care  should  be  taken  that  no  more  pressure  is 
produced  than  is  necessary  to  keep  the  substitute  in  place,  as, 
without  this  precaution,  outward  displacement  of  the  teeth  is 
liable  to  occur,  and  the  appliance,  losing  its  bearing  upon  the 
teeth,  soon  becomes  loosened  and  insecure  in  the  mouth.  The 
result  alluded  to  should  be  particularly  guarded  against  in  the 
case  of  young  subjects,  whose  teeth  are  easily  moved  by  the 
application  of  very  slight  forces. 

Modifications  in  the  Form  of  Plates  for  Partial  Dentures 
Supported  in  the  Mouth  by  Clasps. — The  particular  form  and 
dimensions  of  a  plate  when  clasps  are  used  will  be  mainly 
determined  by  the  number  and  position  of  the  teeth  to  be 
replaced,  and  by  the  location  of  the  natural  organs  to  which  the 
clasps  are  attached.     It  will  be  sufficient  in  this  place  to  indicate 


PARTIAL    DENTURES    RETAINED    BY    CLASPS. 


399 


the  leading  forms  as  they  relate  to  the  substitution  of  the  several 
classes  of  teeth.  In  supplying  the  loss  of  a  superior  central  or 
lateral  incisor,  it  will  be  sufficient  in  many  cases  to  attach  the 
plate  to  either  a  bicuspid  or  molar  on  the  same  side.  If  two 
or  more  of  the  front  teeth,  however,  are  to  be  replaced,  it  is 
better  to  extend  the  plate  on  each  side  of  the  palatal  arch,  and 
attach  to  a  bicuspid  or  molar  (Fig.  483).  In  all  cases  where  it 
is  necessary  to  extend  a  narrow  plate  from  the  extreme  front 
part  of  the  mouth  to  a  single  tooth  situated  posteriorly  in  the 
arch,  the  former  should  be  strengthened  by  soldering  a  narrow 

Fig.  483. 


rim  of  plate  or  half-round  wire  along  the  border  next  the  teeth, 
and  the  clasp  should,  whenever  practicable,  pass  in  front  of  and 
embrace  the  anterior  lace  of  the  tooth  to  which  it  is  applied. 

If  an  anterior  bicuspid  is  to  be  replaced,  the  plate  may  be 
attached  to  the  adjoining  bicuspid,  or  if  both  are  absent,  then  to 
the  first  molar,  or  the  clasp  may  embrace  both  of  the  latter  if 
remaining  and  no  separation  between  them  exists. 

Take  a  case  where  it  is  necessary  to  supply  the  loss  of  the  two 
bicuspids  on  one  side,  and  the  first  bicuspid  and  first  molar  on 
the  opposite,  the  plate  being  attached  to  an  anterior  molar  and 
second  bicuspid.     The  antero-posterior  extension  of  the  plate,  in 


400 


MECHANICAL    DENTISTRY. 


connection  with  the  bicuspid  tooth,  greatly  favors  the  stability  of 
the  substitute,  and,  provided  the  plate  and  clasp  are  accurately 
fitted  to  the  parts,  the  support  afforded  by  a  bicuspid  tooth 
under  such  circumstances  is  equivalent  to  that  furnished  by  a 
clasp  about  a  firm  and  well-formed  molar.  A  base  so  supported 
may  be  made  to  sustain  a  number  of  teeth  with  much  security. 
Either  the  anterior  or  posterior  molars,  if  firm  and  securely 
attached  to  the  jaw,  will  afford  adequate  support  to  a  plate 
replacing  all  of  the  teeth  anterior  to  them.  Even  a  single 
molar  situated  on  either  side  of  the  arch,  if  similarly  circum- 

FiG.  484. 


stanced,  may  be  made  to  sustain,  with  tolerable  firmness,  a 
base  supplying  the  loss  of  all  the  remaining  teeth,  though, 
ordinarily,  it  is  better  to  extract  such  teeth  and  substitute  an  entire 
upper  denture.  In  all  cases,  where  any  considerable  number  of 
teeth  anterior  to  those  clasped  are  to  be  replaced,  and  a  vacuity 
on  the  ridge  exists  posterior  to  the  latter,  the  plate  should  be 
extended  back  and  overlap  the  ridge  (Fig.  484),  the  latter  afford- 
ing a  counter-point  of  resistance  when  traction  is  made  upon  the 
anterior  teeth,  thus  directing  the  forces  applied  more  on  a  line 
with  the  long  axes  of  the  teeth  that  sustain  the  appliance. 

In  Supplying  the  Loss  of  the  Inferior  Molars  and  Bicus- 
pids, or  any  number  of  these  teeth,  the  form  of  plate  represented 


PARTIAL    DENTURES    RETAINED    BY    CLASPS. 


401 


in  Fig.  485  is  generally  employed.  The  parts  of  the  plate  over- 
lapping and  resting  upon  the  ridge  behind  are  connected  with 
each  other  by  a  narrow  strip  of  plate  extending  round  the  ridge, 
hugging  the  lingual  side  of  the  anterior  teeth.  This  latter  por- 
tion of  the  plate  should  be  accurately  swaged  to  the  form  of 
the  gum  on  which  it  rests,  and  should  be  made  narrow  enough 
to  avoid  encroaching  upon  the  reflected  portion  of  mucous 
membrane,  the  glands  beneath  the  tongue,  or  the  frenum  linguae. 
Reinforcing. — To  avoid  wounding  these  parts,  and  to  allow 
them  unobstructed  play,  it  will  be  necessary  to  make  this  portion 
of  the  plate  quite  narrow ;  and  as  a  single  thickness  of  plate 
would  not  impart  adequate 

strength,  it  is   better  prac-  ^'^-  ^^S- 

tice  to  reinforce  or  double 
this  connecting  band — the 
duplicate  band  extending 
back  to  the  lateral  wings 
of  the  plate,  and  crossing 
them  obliquely,  as  indi- 
cated by  the  lines  in  Fig. 
485.  Additional  strength 
will  be  given  by  doubling 
the  entire  plate,  but  this 
is  not  generally  required. 
The  outer  border  of  those 

portions  of  the  plate  overlapping  the  ridge  may  be  turned  up 
to  the  depth  of  from  half  a  line  to  a  line,  to  form  a  groove  or 
socket  for  the  reception  of  the  ends  of  gum  teeth,  or  blocks, 
if  such  are  used;  while  the  inner  margins  should  terminate 
in  a  rounded  edge,  extending  from  heel  to  heel  of  the  plate, 
this  form  being  given  to  it  either  by  turning  the  edge  over  and 
filling  in  the  groove  with  solder,  or  by  soldering  a  narrow  strip 
of  plate  or  half-round  wire  along  the  border.  The  circum- 
stances or  conditions  which  make  the  use  of  clasps  necessary  in 
these  cases,  as  well  as  those,  also,  which  contraindicate  their 
employment,  have  already  been  noticed.  The  practice  of 
extending  a  narrow  band  or  wire  from  the  sides  of  the  plate 
round  the  outer  border  of  the  ridge  in  front  of  the  anterior 
26 


402  MECHANICAL    DENTISTRY. 

teeth,  to  prevent  a  backward  displacement  of  the  base,  is  liable 
to  produce  irritation  and  tenderness  of  the  mucous  membrane 
immediately  over  the  roots  of  the  anterior  teeth,  and  should, 
therefore,  never  be  resorted  to  unless  there  are  no  teeth  remain- 
ing to  which  clasps  may  be  applied. 

If  the  appliance  is  designed  to  restore  the  loss  of  teeth  re- 
cently extracted,  and  where  but  little  or  no  change  has  occurred 
from  absorption  of  the  parts,  the  portions  of  the  plate  which 
pass  in  between  the  adjoining  teeth  should  terminate  a  line  or 
more  within  the  outer  circle  of  the  remaining  teeth ;  and  where 
the  space,  if  it  happens  in  the  front  part  of  the  mouth,  admits 
of  two  or  more  teeth,  the  edges  of  the  extended  portion  of 
plate  should  be  scalloped  in  correspondence  with  the  festoons 
of  the  gum,  as  seen  in  Fig.  483.  In  such  cases,  plain  or  plate 
teeth,  by  which  is  meant  those  which  represent  only  the  crowns 
of  the  natural  organs,  should  be  employed ;  these,  resting  on 
the  edge  of  the  plate,  will  overlap  somewhat,  with  their  ante- 
rior edges  resting  directly  upon  the  gum  in  front,  taking  the 
place  occupied  by  the  crowns  of  the  extracted  teeth.  On 
the  other  hand,  if  sufficient  time  has  elapsed  after  the  extrac- 
tion of  the  teeth  to  permit  the  changes  in  the  form  of  the  ridge 
to  occur  incident  to  partial  or  complete  absorption  of  the  parts, 
and  a  greater  or  less  concavity  exists  between  and  above  the 
teeth  on  the  outside  of  the  jaw,  the  plate,  where  it  passes  into 
the  interspace,  should  extend  some  distance  over  the  border  of 
the  ridge. 

Swaging  the  Plate. — Having  determined  upon  the  proper 
form  and  dimensions  of  the  plate  for  any  given  case,  its  outlines 
may  first  be  traced  upon  the  model ;  from  this  an  exact  pattern 
in  lead  may  be  obtained,  or  the  pattern  may  be  sufficiently  ample 
to  partially  overlap  the  cut  extremities  of  the  teeth  when  the 
latter  are  not  represented  upon  the  die,  having  been  previously 
cut  from  the  model,  as  shown  in  Fig.  68.  The  outlines  of  the 
pattern  are  then  traced  upon  the  plate  of  gold  or  other  metal 
used  for  the  base.  The  redundant  portions  of  plate  are  then  cut 
away  with  plate  shears  and  forceps,  and  the  edges  trimmed 
smooth  with  a  file.  A  very  convenient  and  almost  indispensable 
instrument  for  cutting  away  the  plate   in  conformity  with  the 


PARTIAL    DENTURES    RETAINED    BY    CLASPS. 


403 


palatal  curvatures  of  the  teeth,  is  the  plate  forceps  as  exhibited 
in  Fig.  486. 

The  plate  cut  to  the  proper  form  is  now  placed  upon  the  die  and 
brought  as  nearly  as  possible  into  adaptation  with  a  wooden  or 
horn  mallet ;  it  is  then  placed  between  the  die  and  counter,  the 
latter  resting  on  an  anvil  or  other  equally  resisting  surface,  when 
the  two  metallic  pieces  are  brought  forcibly  together  with  a  few 
steady  and  well-directed  blows  of  a  heavy  hammer.  Tilting  of 
the  die,  resulting  sometimes  unavoidably  from  a  one-sided  blow, 
may  be  obviated  by  placing  a  cone-shaped  piece  of  cast-iron, 
brass,  or  zinc  over  the  die,  the  base  of  the  cone  resting  on  the 
back  of  the   die ;   by  this    expedient  the  force    of   the  blow  is 

Fig.  486. 


equalized  and  concentrated  more  directly  over  the  die.  The 
metallic  swages  should  at  first  be  brought  cautiously  together, 
and  should  be  separated  after  the  first  blow  or  two,  to  enable  the 
manipulator  to  detect  and  remedy  any  malposition  of  the  plate 
before  it  becomes  intractable  from  continued  swaging.  If,  in  the 
process  of  stamping,  any  portion  of  the  plate  is  found  cracking 
or  parting,  its  further  extension  at  that  point  may  be  prevented 
by  flowing  a  little  solder  at  the  termination  of  the  fissure. 

Annealing  the  Plate. — During  the  progress  of  swaging  the 
plate  should  be  frequently  annealed,  which  is  done  by  bringing 
it  to  a  full  red  heat  under  the  blowpipe  or  by  placing  it  in  the 
furnace  ;  the  plate  is  thus  rendered  more  pliant  and  can  be  more 
readily  and  perfectly  forced  into  adaptation  to  the  irregularities 
on  the  face  of  the  die. 

If,  after  somewhat  protracted  swaging,  the  plate  is  not  conformed 


404  MECHANICAL    DENTISTRY. 

perfectly  to  the  face  of  the  die,  another  and  unused  counter 
should  be  substituted  for  that  in  use ;  and,  indeed,  it  is  better  in 
all  cases  to  have  duplicate  copies  both  of  the  die  and  counter  in  re- 
serve with  which  to  complete  the  swaging,  inasmuch  as  more  or  less 
deformity  of  both  swages  unavoidably  occurs  before  the  plate  is 
brought  into  very  accurate  coaptation  with  the  die.  The  stamp- 
ing conducted  thus  far,  the  plate  may  be  applied  to  the  plaster 
model,  and  if  found  too  full  at  any  point,  it  should  be  trimmed 
with  a  file  to  the  exact  dimensions  required.  The  margins  of 
the  plate  adjoining  the  necks  of  the  teeth  should  be  permitted 
either  to  lie  closely  to  them,  or  should  be  cut  away,  leaving  a 
space  equal  to  a  line  or  more  between  the  plate  aijd  the  teeth  ; 
for  if  but  a  very  narrow  line  of  uncovered  gum  remains  at  these 
points,  injury  to  the  parts  immediately  surrounding  the  necks 
of  the  teeth  is  more  liable  to  occur  from  strangulation  of  the 
interposed  gum  than  if  the  plate  were  further  removed  from  the 
teeth  or  rested  directly  against  them. 

Adjusting  and  Strengthening  the  Projections  or  Tongues 
of  the  Plate. — If  the  portion  of  the  plate  which  passes  in 
between  the  remaining  teeth  is  quite  narrow,  as  where  but  a 
single  tooth  is  to  be  supplied,  it  should  be  strengthened  by 
wiring  the  edges  or  doubling  the  plate  at  such  point.  It  is  also 
advisable  in  many  cases,  in  order  to  provide  more  perfectly 
against  fracture  or  distortion  of  the  base  in  mastication,  to  wire 
or  double  the  entire  border  of  the  plate  adjoining  the  necks  of 
the  teeth.  Narrow  bands  of  gold  resting  against  the  necks  of  the 
teeth,  constructed  and  adjusted  after  the  manner  of  stay  clasps,  are 
sometimes  soldered  to  the  edge  of  the  plate  next  the  teeth  ;  but 
unless  the  substitute  is  frequently  cleansed,  as  well,  also,  as  the 
teeth  to  which  they  are  applied,  serious  injury  is  likely  to  be 
inflicted  upon  the  teeth  implicated. 

The  edges  of  those  parts  of  the  plate  occupying  the  vacuities 
on  the  ridge  should  be  filed  thin  to  admit  of  a  more  accurate 
adaptation  of  the  artificial  with  the  natural  gum,  and  should  not, 
as  before  observed,  ordinarily  extend  beyond  the  outer  circle  of 
the  contiguous  teeth,  allowing  the  gum  extremity  of  the  artificial 
tooth  to  overlap  and  rest  directly  on  the  natural  gum  above. 
If,  however,  the  concavity  between  and  above  the  teeth  on  the 


PARTIAL    DENTURES    RETAINED    BY    CLASPS.  405 

external  border  of  the  ridge  is  considerable,  the  interdentinal 
portions  of  plate  should  overlap  the  border  completely  and 
underlie  the  porcelain  gum. 

Adjusting  Clasps  to  the  Plate. — Having  proceeded  thus 
far  in  the  operation,  the  plate  and  clasps  should  next  be  united 
to  each  other,  and  the  titiHty  and  comfort  of  the  appliance  in  the 
numtJi,  as  zvell  as  the  safety  of  the  natural  organs  used  for  the  pur- 
pose of  support,  zvilL  depend  in  a  great  measure  upon  the  accurate- 
ness  of  the  relation  of  the  several  parts  of  the  appliance  to  the 
organs  of  the  mouth;  it  being  a  matter  of  primary  importance 
that  the  various  parts  of  the  substitute  should  be  so  adjusted  to 
the  remaining  teeth — especially  those  to  which  the  clasps  are 
applied — and  the  ridge  and  palate,  that  it  shall  not,  in  any 
material  degree,  act  as  a  retractor  upon  the  organs  of  support, 
or  furnish  interspaces  for  the  lodgment  of  food,  while  at  the 
same  time  it  should  be  so  fitted  as  to  be  easily  removed  and 
applied  by  the  patient. 

Manner  of  Securing  Clasps  to  the  Plate. — The  clasps 
having  been  fitted  to  the  plaster  teeth  and  the  base  swaged  to 
the  form  of  the  palatal  arch  and  ridge,  the  plate  is  placed  in  its 
proper  position  in  the  mouth  and  an  impression  in  wax  taken 
of  the  latter  with  the  plate  in  place.  The  impression,  with  the 
plate  adhering,  is  then  removed  from  the  mouth,  its  surface 
oiled,  and  a  model  obtained  in  the  manner  heretofore  described. 
If,  in  separating  the  model  and  impression,  the  plate  adheres  to 
the  latter,  it  should  be  detached  and  adjusted  to  the  model  and 
the  clasps  arranged  upon  the  plaster  teeth.  The  plate  and 
clasps  may  now  be  attached  to  each  other  temporarily,  with 
adhesive  wax,  in  the  relation  they  occupy  on  the  model,  and 
then  removed  carefully  and  the  clasps  and  palatal  face  of  the 
plate  embedded  in  a  mixture  of  nearly  equal  parts  of  plaster,  sand, 
and  asbestos.  Before  uniting  the  two  pieces  on  the  model  with 
wax,  however,  the  ends  of  the  clasps  should  be  slightly  spread 
apart,  in  order  that  they  may  part  readily  from  the  plaster  teeth, 
without,  in  any  degree,  changing  their  exact  relation  to  the 
plate ;  in  doing  which,  it  should  be  observed  that  all  parts  of  the 
clasps  which  are  to  be  united  to  the  plate  should  remain  in  close 
contact  with  the  plaster  teeth.     After  the   plaster  mixture,  in 


406  MECHANICAL    DENTISTRY. 

which  the  plate  and  clasps  are  embedded,  has  become  sufificiently 
hard,  the  portions  of  wax  which  temporarily  united  the  latter 
should  be  removed,  and  the  surfaces  of  the  clasps  and  plate, 
where  they  unite  with  each  other,  coated  with  borax  ground  in 
water  to  the  consistency  of  cream  ;  small  pieces  of  solder  are 
then  placed  along  the  lines  of  contact,  the  investment  heated  in 
the  furnace  until  the  plate  acquires  a  full  red  heat,  when  it  is 
removed,  placed  upon  a  suitable  holder,  and  the  solder  fused 
with  the  blowpipe. 

Whenever  the  form  and  inclination  of  the  teeth  to  be  clasped 
are  not  fairly  represented  on  the  model,  owing  to  dragging  or 
displacement  of  the  wax  in  withdrawing  the  impression,  the 
difficulties  of  securing  a  proper  relative  adjustment  of  the  several 
parts  of  the  appliance  will  be  increased;  but  either  of  the  follow- 
ing methods,  if  carefully  and  accurately  manipulated,  will  secure 
accurate  results: — 

1.  Plaster-of-Paris  or  modeling  compound  may  be  substituted 
for  wax  when  taking  an  impression  with  the  plate  in  the  mouth. 
With  the  proper  use  of  these  materials,  the  exact  form  and 
inclination  of  the  teeth  will  be  better  preserved;  and  when 
employed  they  should  be  filled  in  with  plaster  for  the  model 
immediately  after  removing  them  from  the  mouth.  The  subse- 
quent steps  in  the  operation  are  precisely  similar  to  those 
described  when  wax  is  used. 

2.  Another  method  is  to  adjust  the  clasps  and  plate  to  the 
parts  in  the  mouth,  attach  them  temporarily  in  their  proper 
relation,  and  remove,  invest,  and  solder  in  the  usual  way.  This 
may  be  accomplished  in  the  following  manner:  First,  spread 
apart  the  ends  of  the  clasp  somewhat  to  permit  it  to  be  easily 
removed  from  the  tooth ;  place  this  upon  the  tooth  in  the 
mouth  to  be  clasped  ;  then  adjust  the  plate,  and  attach  the 
two  to  each  other  by  pressing  a  piece  of  stiff,  adhesive  wax 
in  against  the  clasp  and  plate  where  they  unite  ;  harden  the  wax 
by  placing  against  it,  for  a  few  minutes,  the  end  of  a  napkin 
moist  with  cold  water ;  then  remove  the  plate  and  clasp  carefully 
from  the  mouth,  and  invest  and  solder  as  before.  The  plate, 
with  one  clasp  permanently  attached,  is  now  placed  back  in  the 
mouth,  and  the  second  clasp  adjusted  to  the  tooth  on  the  oppo- 


PARTIAL    DENTURES    RETAINED    BV    CLASPS.  407 

site  side  in  the  manner  before  alluded  to ;  this  is  then  tempo- 
rarily fastened  to  the  plate  and  otherwise  treated  in  like  manner 
as  the  one  first  described.  If  the  teeth  to  be  clasped  are  favor- 
ably formed  and  regularly  arranged  in  the  arch,  both  clasps  may, 
at  the  same  time,  be  temporarily  attached  to  the  plate  in  the 
first  instance ;  if  not,  it  will  be  impracticable  to  remove  them 
from  the  teeth  without  disturbing  the  wax  and  changing  their 
relation  to  the  base  and  the  teeth  clasped.  The  additional  labor 
and  consumption  of  time  incident  to  a  separate  attachment  of 
the  clasps  will,  in  proportion  as  they  secure  better  results, 
amply  reward  the  operator  for  his  painstaking. 

Plaster  is  sometimes  substituted  for  wax  in  this  process ;  in 
which  case  it  is  introduced  into  the  mouth  on  a  small  piece  of 
wax  or  sheet  lead  and  pressed  gently  against  the  uniting  por- 
tions of  the  plate  and  clasp,  and  allowed  to  remain  until  suffi- 
ciently hard.  Any  superfluous  portions  around  the  tooth  that 
may  hinder  the  easy  removal  of  the  clasp  should  now  be  cut 
away,  when  the  pieces  so  attached  to  each  other  are  removed 
from  the  mouth.  A  separation  of  the  plaster  from  the  clasp  or 
plate,  or  both,  may  occur  when  removing  the  latter;  in  this  case 
the  several  parts  may  be  readily  and  accurately  adjusted  to  each 
other  again  in  their  exact  relation  when  out  of  the  mouth,  as 
the  latter  will  be  plainly  indicated  by  the  impression  made  by 
the  plate  and  clasp  in  the  plaster.  Being  readjusted,  they  may 
be  further  secured  by  sticking  them  together  with  a  little  soft- 
ened wax,  when  they  are  invested,  the  temporary  fastening  of 
plaster  removed,  and  the  pieces  united  by  soldering.  The  use 
of  plaster  in  these  cases  is  due  to  Dr.  Lester  Noble,  and  unques- 
tionably possesses  many  advantages  over  wax  for  the  purpose, 
as  the  latter  is  liable,  even  with  the  most  skilful  manipulation, 
to  become  displaced  in  removing  it  from  the  mouth  ;  and  this 
change,  when  it  occurs,  not  being  indicated  by  inspection  of  the 
wax,  is  incapable  of  timely  correction. 

3.  Still  another  m.ethod  is  that  contrived  by  Dr.  Fogle  and 
described  by  Dr.  Cushman  in  the  tenth  volume  of  the  American 
Journal  of  Dental  Science.  It  consists  in  securing  the  proper 
relation  of  the  clasps  to  the  teeth  in  the  mouth  by  the  use,  in 
the  first   instance,  of  what  are  termed  "  temporary  fastenings." 


408  MECHANICAL    DENTISTRY. 

The  plate  and  clasps  are  first  applied  to  the  model,  and  are  then 
connected  by  a  narrow  strip  of  plate  or  piece  of  wire  bent  in  the 
form  of  a  bow,  the  concavity  facing  the  model,  one  end  of  which 
is  soldered  to  the  palatal  side  of  the  clasp,  and  the  other  to  a 
contiguous  point  upon  the  plate,  as  exhibited  in  Fig.  487,  and 
the  pieces  thus  temporarily  united  are  removed  from  the  model 
and  adjusted  to  the  parts  in  the  mouth.  If  the  position  of  the 
clasps  is  found  in  any  respect  faulty,  they  can  be  easily  and  ac- 
curately adapted  to  the  walls  of  the  teeth  by  bending  or  twisting 
the  connecting  strip  in  any  desired  direction  with  pliers  or 
other    instruments    suitable    for    the    purpose.       This    accom- 

FiG.  487. 
y7\ 


w 


plished,  the  plate  and  clasps  are  removed,  and  the  operation  of 
permanently  uniting  the  clasps  to  the  plate  performed  in  the 
usual  manner. 

In  the  use  of  partial  dentures,  there  is  always  increased  liability 
to  injury  of  the  soft  parts  by  reason  of  pressure  being  concen- 
trated upon  limited  or  circumscribed  portions  of  the  alveolar 
ridge  embraced  in  interdental  spaces,  thereby  diminishing  resist- 
ance to  the  pressure  of  the  plate  at  such  points.  As  a  conse- 
quence, the  latter  is  forced  into  the  soft  tissues,  producing  more 
or  less  irritation  and  inflammation,  and  consequent  tenderness 
and  pain  on  pressure,  and,  generally,  either  partial  denudation 
of  the  necks  of  the  natural   teeth  abutting  upon  the  interdental 


PARTIAL    DENTURES    RETAINED    BY    CLASPS.  4O9 

spaces,  or  strangulation,  congestion,  and  hypertrophy  of  the  gum 
in  immediate  contact  with  them. 

A  simple  device,  by  which  the  results  alluded  to  may  be  ob- 
viated, consists  in  attaching  to  the  clasps,  above  or  below,  a 
strip  or  spur  of  gold  at  suitable  points,  long  enough  to  overlap 
or  rest  upon  the  masticating  surface  of  the  tooth  clasped,  form- 
ing a  hook  or  partial  crown  cap.  These  will  afford  fixed  points 
of  resistance  to  pressure  and  effectually  prevent  the  plate  im- 
pinging upon  the  underlying  tissues.  The  same  expedient  may 
be  adopted  also,  in  the  case  of  partial  dentures  retained  by  ad- 
hesion or  atmospheric  pressure,  by  attaching  similar  gold  spurs 
or  caps  to  the  border  of  the  plate  at  suitable  points  contiguous 
to  the  bicuspids  and  molars. 

Fig.  488.  Fig.  489. 


Charles  Rathbun,  of  London,  England,  relates,  in  the  Dental 
Cosmos  of  December,  1886,  a  method  of  constructing  partial 
pieces  which  embodies  the  same  principle  of  crown-support  as 
described  above,  the  essential  details  of  which  are  here  given  : — 

"  In  Fig.  488  we  have  the  first  bicuspid  standing ;  the  second 
bicuspid  and  cuspid  in  that  case  filling  the  role  of  the  lateral, 
missing  from  its  position.  The  bicuspid  is  pear-shaped,  its  larg- 
est diameter  being  just  below  the  grinding  surface,  and  the  molar 
is  a  trifle  under-cut.  A  No.  7  or  8  English  gauge  gold  plate, 
struck  from  a  model  made  from  a  modeling  compound  impres- 
sion, would  not  touch  the  necks  of  either  the  bicuspid  or  molar, 
owing  to  the  fact  that  these  teeth  would  '  draw '  a  little  in  the 
impression,  and  it  should  be  fitted  over  the  shoulder  at  the  neck 
on  the  lingual  side  of  the  cuspid,  left  clear  of  it  at  the  distal  side, 
and  have  a  stay  or  clip   resting  just  above   the  prominence  on 


410  MECHANICAL    DENTISTRY. 

that  side  of  the  tooth.  A  band  should  be  soldered  to  the  plate 
at  the  lingual  side  of  the  bicuspid,  to  grasp  that  tooth  at  its  larg- 
est point,  viz.,  about  one-third  of  the  distance  from  the  grinding 
surface  to  the  neck  ;  also,  a  band  fitted  to  the  molar  to  reach 
from  about  the  middle  of  the  lingual  side  far  enough  around  the 
mesial  face  to  clasp  over  the  prominence  at  the  mesio-buccal 
aspect  of  the  tooth  ;  this  band  to  be  fitted  to  grasp  the  tooth  at 
its  fullest  part,  as  in  the  case  of  the  bicuspid.  (See  Fig.  489.) 
Wires  or  clasps  at  the  necks  of  teeth  of  this  class  do  no  end  of 
damage  to  the  teeth,  and  are  open  to  the  great  objection  that  a 
case  may  go  in  very  hard,  and  yet  when  the  clasps  are  past 
the  large  part  of  the  teeth  the  case  is  quite  loose  and  shaky. 
The  bands  I  have  described  do  not  bear  on  the  teeth  at  all  until 
the  case  is  within  about  a  line  of  its  place,  and  then  each  one 
bears  on  its  own  tooth  irrespective  of  the  others,  and,  be  it  borne 
in  mind,  touches  the  tooth  at  a  point  where  the  chance  of  decay 
is  simply  infinitesimal.  If  a  porcelain  cuspid  and  bicuspid  be 
ground  in  properly,  the  clasps  will  not  be  visible  externally, 
which  cannot  be  said  of  the  broad  gold  band  carried  across  the 
buccal  face  of  the  natural  tooth." 


CHAPTER   VII. 

PARTIAL   DENTURES   SUPPORTED   BY   ATMOSPHERIC 
PRESSURE   OR   ADHESION. 

The  method  of  attaching  partial  sets  of  teeth  to  the  superior 
jaw  by  means  of  atmospheric  pressure,  or  by  adhesion,  is  much 
more  generally  practised  than  formerly,  and  whenever  the  con- 
dition of  the  soft  parts  of  the  mouth,  the  general  configuration 
of  the  palatal  arch,  and  the  antagonism  or  occlusion  of  the 
artificial  with  the  natural  teeth  favor  its  adoption,  there  are  good 
and  sufficient  reasons  why  either  of  these  forces  should,  in  all 
practicable  cases,  be  utilized  in  preference  to  the  use  of  clasps 
for  purposes  of  attachment. 

Modifications  in  the  Form  of  the  Base. — If  vacuities  exist 
at  various  points  on  the  ridge,  the  plate  on  which  the  teeth  of 
replacement  are  mounted  should  be  ample  in  its  dimensions, 
covering  nearly  or  quite  all  of  the  hard  palate.  The  general 
form  of  the  base,  where  several  teeth  scattered  throughout  the 
arch  are  required,  is  shown  in  Fig.  490.  In  most  cases,  whether 
but  one  or  a  greater  number  of  teeth  are  to  be  replaced, 
increased  adherence  and  stability  of  the  substitute  will  be  better 
secured  by  permitting  the  plate  to  cover  the  larger  portion  of 
the  roof  of  the  mouth ;  though,  in  cases  that  present  the  best 
form  of  the  vault,  a  diminished  surface  may  be  given  to  the  base 
with  equally  satisfactory  results.  In  the  substitution  of  a  single 
incisor,  for  example,  it  will  frequently  be  sufficient  to  employ  a 
very  small  plate  covering  only  a  part  of  the  anterior  sloping 
wall  of  the  palate.  In  the  latter  case  the  plate  used  may  be  very 
thin,  say  No.  30  standard  gauge  ;  it  will  thus  impede  the  move- 
ments of  the  tongue  less,  and  may  be  swaged  more  accurately 
to  the  parts.  If  constructed  with  an  air-chamber,  the  latter 
should  be  quite  shallow. 

A  somewhat  anomalous  form  oC  atmospheric-pressure  plate 
employed  in  the   substitution   of  one  or  two  bicuspid  teeth  on 

411 


412 


MECHANICAL    DENTISTRY. 


each  side  is  described  by  Professor  Taft,^  the  design  of  which  is 
to  secure  in  such  cases  increased  stability  of  the  substitute,  while 
much  of  the  palatal  arch  is  left  uncovered.  It  consists,  of  two 
lateral  cavity  plates  accurately  adjusted  to  the  sloping  walls  of 
the  palate  on  each  side,  immediately  adjoining  and  partly  occupy- 
ing the  spaces  to  be  supplied.  These  lateral  plates  may  be  made 
as  large  as  a  dime,  or  somewhat  larger,  and  of  an  elliptical  shape 
if  both  bicuspids  on  the  same  side  are  to  be  replaced,  and  are  con- 
nected with  each  other  by  a  narrow  band  of  gold  plate,  two  lines 
or  more  in  width,  having  an  anterior  curvature,  and  resting  on  the 


front  wall  of  the  palate,  two  or  three  lines  behind  the  anterior 
teeth.  The  entire  appliance  may  be  constructed  from  a  single 
piece  of  gold  plate  swaged  accurately  to  the  parts  ;  or  the  lateral 
plates  and  connecting  band  may  be  separately  swaged  and  secured 
in  their  proper  relation  to  each  other  in  the  mouth  with  wax  or 
plaster,  when  they  are  carefully  removed,  invested,  and  soldered 
together;  it  should  then  be  reswaged  to  correct  any  change  of 
relation  that  may  have  happened  during  the  concluding  manipu- 
lations. The  liability  of  the  plate  to  ride  upon  the  central  and 
raised  portion  of  the  palate,  when   pressure  is  made  upon  one 


*  Dental  Register  of  the  West,  vol.  xui,  p.  112. 


PARTIAL    DENTURES    HELD    BY    ATMOSPHERIC    PRESSURE.     413 

side,  throwing  the  plate  off  from  the  ridge  on  the  other,  as  in  the 
case  of  a  base  extending  across  the  arch,  is  in  a  great  degree 
obviated  by  the  method  just  described. 

Manner  of  Forming  an  Air  Chamber. — Atmospheric- 
pressure  plates  for  partial  cases  are  constructed  with  a  central 
air  chamber;  in  which  case,  the  part  of  the  model  representing 
the  chamber  may  be  formed  in  either  of  the  ways  mentioned  in 
the  chapter  on  "  Plaster  Models."  The  model  prepared,  the 
form  of  the  plate  to  be  used  is  first  indicated  thereon,  and  from 
this  a  pattern  in  sheet  lead  is  obtained,  which  is  placed  on  the 
plate  of  gold  or  other  metal,  and  its  outlines  traced  with  a 
pointed  instrument ;  the  redundant  portions  are  then  cut  away 
with  plate  shears  and  forceps.  The  plate  is  now  placed  on  the 
die  and  brought  as  nearly  as  possible  into  adaptation  to  the  latter 
with  the  mallet  and  pliers ;  it  is  then  interposed  between  the  die 
and  the  counter,  and  swaged  until  it  conforms  perfectly  to  the 
face  of  the  former,  annealing  the  plate  frequently  to  render  it 
more  pliant  and  manageable  under  the  hammer. 

The  Use  of  a  Tracer  in  the  Swaging  Process. — Unless  the 
plate  used  is  purer  and  thinner  than  is  generally  employed,  or 
than  is  consistent  with  the  required  strength,  it  will  fail  to  be 
forced  perfectly  into  the  groove  around  the  chamber  by  the  pro- 
cess of  swaging  alone ;  a  more  definite  border,  however,  may  be 
formed  by  forcing  the  plate  in  at  this  place  with  a  small,  smooth- 
faced stamp  or  tracer,  shaped  to  the  angle  of  the  groove,  pass- 
ing round  the  chamber  and  carefully  forcing  the  plate  in  with 
the  stamp  and  a  small  hammer  or  mallet  until  a  somewhat  sharp 
and  abrupt  angle  is  obtained  to  the  palatal  edge  of  the  chamber. 
After  the  chamber  is  as  perfectly  formed  as  possible  in  this  way, 
the  plate  should  be  well  annealed  and  again  swaged  to  correct 
any  partial  deformity  occasioned  by  stamping  the  chamber. 

The  Soldered  Air  Chamber. — A  still  more  perfectly  defined 
angle  may  be  given  to  the  borders  of  the  chamber  in  the  follow- 
ing manner  :  After  swaging  the  plate  sufficiently  to  indicate  the 
exact  position  and  form  of  the  chamber,  the  portion  forming  the 
latter  should  be  separated  from  the  main  plate  by  completely 
dividing  it  with  a  saw,  or  small,  sharp,  chisel-shaped  instrument, 
cuttinsf  on  a  line  with  the  groove  around  the  chamber  until  the 


414  MECHANICAL    DENTISTRY. 

latter  is  entirely  separated.  The  cut  portion  of  the  main  plate 
is  then  trimmed  evenly  with  a  file,  being  careful  not  to  enlarge 
the  opening  more  than  is  required  to  remove  the  irregularities 
of  the  edge  formed  in  cutting.  The  plate,  with  its  central 
portion  removed,  is  then  placed  upon  the  die,  when  a  separate 
piece  of  gold  cut  to  the  general  form  of  a  chamber,  but  some- 
what larger  than  the  opening  in  the  main  plate,  is  adjusted  over 
the  chamber,  and  struck  up  with  the  plate  until  the  overlapping 
portions  of  the  central  piece  are  forced  down  upon  the  plate  around 
the  margins  of  the  chamber.  It  is  not,  however,  always  necessary 
to  employ  a  separate  piece  of  gold  for  the  chamber,  as  the  central 
portion  cut  from  the  plate  in  the  first  instance  maybe  sufficiently 
enlarged  for  the  purpose.  This  is  accomplished  by  first  flattening 
out  the  detached  portion,  annealing  it,  and  then  passing  succes- 
sive portions  of  its  edges  a  sixteenth  of  an  inch  or  more  between 
the  rollers,  the  latter  being  sufficiently  approximated  to  produce 
a  perceptible  thinning  of  the  margins.  When  the  entire  border 
of  the  chamber  piece  has  been  thus  attenuated  and  extended,  it 
will  be  found  so  much  enlarged  that,  when  adjusted  to  the  die 
and  swaged  in  connection  with  the  main  plate,  its  borders 
will  overlap  and  rest  upon  the  margins  of  the  opening  in  the 
base,  as  in  the  other  case. 

The  portions  of  the  plate  and  cut  chamber  lying  in  contact 
are  now  coated  with  borax  and  pieces  of  solder  placed  along 
the  line  of  union  on  the  lingual  side  of  the  plate,  when  the  two 
pieces,  being  transferred  to  a  bed  of  charcoal,  are  permanently 
united  by  flowing  the  solder  with  a  blowpipe.  Sufficient  heat 
should  be  applied  to  induce  an  extension  of  the  solder  between 
the  two  portions  of  plate,  filling  up  completely  the  gap  between 
them  to  the  edge  of  the  orifice  in  the  main  plate,  forming,  at  this 
point,  a  square  and  well-defined  angle  to  the  margins  of  the 
chamber. 


CHAPTER  VIII. 

METHOD  OF  OBTAINING  AN  ANTAGONIZING  MODEL  FOR 
PARTIAL  DENTURES;-  SELECTING,  ARRANGING  AND  AN- 
TAGONIZING THE  TEETH  ;  INVESTING,  ADJUSTING  STAYS, 
SOLDERING,  ETC. 

Having  constructed  the  plate  or  base  to  be  used  as  a  support 
for  partial  sets  of  teeth  in  either  of  the  ways  described  in  the 
preceding  chapter,  it  will  be  necessary,  before  arranging  the 
teeth  on  the  plate,  to  secure  an  accurate  representation  of  all  the 
remaining  natural  teeth  of  both  jaws  in  plaster,  preserving 
accurately  the  relation  which  these  organs  bear  to  each  other  in 
the  mouth.  This  is  effected  by  what  is  called  an  antagonizing 
model,  and  may  be  secured  in  the  following  manner  : — 

Taking  the  "Bite." — A  roll  or  strip  of  adhesive  wax  is  first 
attached  to  the  lingual  border  of  the  plate,  and  its  adhesion 
secured  by  holding  the  opposite  side  of  the  plate  for  a  moment 
over  the  flame  of  a  spirit  lamp.  The  wax  used  for  articulating 
purposes  should  be  harder  and  more  tenacious  than  plain  bees- 
wax, and  may  be  compounded  from  the  following  formula: — 

Beeswax, i  pound. 

Gum  mastich, 2  ounces. 

Spanish  whiting, , i  ounce. 

The  wax  is  first  melted  in  a  shallow  vessel,  and  the  mastich, 
finely  pulverized,  gradually  added,  and  then  the  whiting,  stirring 
constantly  until  thoroughly  incorporated.  The  rim  of  wax 
being  arranged  on  the  plate,  all  superfluous  portions  overhang- 
ing the  margins  occupied  by  the  remaining  teeth  are  cut  away ; 
the  plate  may  then  be  placed  on  the  model  and  the  wax  again 
trimmed,  leaving  it  somewhat  fuller  than  the  outer  circle  of  the 
teeth,  and  from  one  to  three  lines  longer  than  those  immediately 
adjoining  the  spaces.  The  plate,  with  the  wax  attached,  is  then 
placed  in  its  proper  position  in  the  mouth,  and  the  patient 
instructed  to  close  the  jaws  naturally  until  the  remaining  teeth 

415 


4l6  MECHANICAL    DENTISTRY. 

meet;  one-third  or  more  of  the  crowns  of  the  opposing  teeth 
opposite  the  spaces  will  thus  be  imbedded  in  the  wax.  A  still 
fuller  impression  of  the  opposing  teeth  may  be  obtained,  if 
desired,  by  pressing  the  edges  of  the  wax  down  upon  the  crowns 
with  the  finger. 

The  Mesial  Line. — If  a  series  of  anterior  teeth  are  to  be 
replaced,  the  mesial  line  of  the  mouth  in  front  should  be  indi- 
cated upon  the  wax  by  drawing  a  line  vertically  across  the  latter 
to  serve  as  a  guide  in  the  arrangement  of  the  central  incisors  and 
adjoining  teeth.  The  plate  and  wax  are  then  carefully  removed 
from  the  mouth  and  again  placed  upon  the  plaster  model,  the 
latter  having  been  previously  obtained  from  an  impression  of 
the  parts  with  the  plate  in  the  mouth. 

Securing  the  Antagonizing  Models. — The  method  of  secur- 
ing the  antagonizing  models  as  practised  by  many  is  to  place  the 
model  on  a  slip  of  paper  with  the  plate  and  wax  upward,  and 
the  heel  of  the  model  extended  from  one  to  two  inches  pos- 
teriorly to  form  an  articulating  surface  for  the  remaining  portion 
of  the  antagonizing  model.  The  added  portion  of  plaster  may 
be  confined  by  a  narrow  strip  of  wax  or  sheet-lead  extending 
back  upon  each  side  of  the  model,  into  which  a  batter  of  plaster 
is  poured  to  the  depth  of  half  or  three-fourths  of  an  inch. 
When  hard,  the  edges  and  upper  surface  of  the  added  plaster 
should  be  trimmed  smooth,  and  a  crucial  groove,  or  two  or 
three  conical-shaped  holes,  cut  in  the  surface  of  the  latter  to 
secure  a  fixed  and  definite  relation  of  the  two  parts  of  the 
model.  The  articulating  surface  is  then  varnished  and  oiled  to 
prevent  the  next  portion  of  plaster  from  adhering ;  the  imprints 
of  the  teeth  in  the  wax  are  also  oiled.  The  open  space  looking 
into  the  palatal  vault  should  be  closed  with  a  sheet  of  softened 
wax  to  prevent  the  next  portion  of  plaster  from  flowing  into  the 
cavity  underneath.  A  batter  of  plaster  is  now  poured  carefully 
upon  the  exposed  surface  of  the  wax,  filling  the  imprints  of  the 
teeth  perfectly,  and  extending  back  upon  the  heel  of  the  model 
until  it  acquires  a  depth  of  half  an  inch  or  more.  When  suffi- 
ciently hard,  the  two  sections  of  the  model  are  separated,  super- 
fluous portions  trimmed  away,  and  the  entire  surface  of  both 
pieces  glazed  with  varnish,  and  if  the  manipulations  have  been 


SELECTING,    ARRANGING    AND    ANTAGONIZING    THE    TEETH.    417 

accurate,  this  simple  contrivance  will  exhibit  all  the  parts  repre- 
sented in  plaster  in  precisely  the  same  relative  position  which 
they  occupy  in  the  mouth.  The  writer  feels,  however,  that  a 
more  elegant  and  accurate  method  of  securing  the  antagonizing 
model,  is  to  take  a  full  impression  of  the  antagonizing  teeth 
in  wax  or  modeling  compound.  Secure  a  plaster  cast  from 
same  and  adjust  the  two  models  properly  upon  an  articulator, 
as  shown  in  Fig.  491. 

Fig.  491. 


Selecting,  Arranging,  and  Antagonizing  the  Teeth. — The 
teeth  of  replacement  should  harmonize,  as  nearly  as  possible,  in 
size,  configuration,  and  color,  with  those  remaining  in  the  mouth  ; 
and  when  selecting  teeth  for  any  given  case,  the  operator  should 
be  provided  with  a  sufficient  number  of  sample  teeth  to  meet 
every  requirement,  by  comparison,  in  respect  of  the  various  tints 
or  delicate  shades  of  color  characteristic  of  the  natural  teeth 
and  gums.  The  required  size  and  form  of  the  artificial  teeth  may 
be  determined  with  tolerable  accuracy  by  a  comparison  with  those 
on  the  plaster  model,  but  the  form  or  figure  more  certainly  by  a 
careful  inspection  of  those  in  the  mouth. 
27 


41  8  MECHANICAL    DENTISTRY. 

Although  there  are  almost  limitless  varieties  of  manufactured 
teeth,  both  as  respect  form  and  color,  it  is  not  always  possible, 
in  partial  cases,  to  obtain  such  as  will  harmonize  with  the 
natural  teeth.  As  to  form,  a  much  closer  resemblance  to  the 
natural  organs  in  immediate  relation  with  those  of  replacement 
can  be  obtained  by  cutting  away  more  or  less  freely  from  the 
cutting  edges  of  the  incisors,  and  the  cusps  of  bicuspids  and 
molars,  in  cases  where  the  natural  teeth  are  much  worn.  The 
ground  surfaces  may  afterward  be  polished  with  pumice  on  a 
buff,  and  finished  with  rotten-stone  and  oil.  The  exigencies  of 
practice,  in  respect  of  partial  sets,  will  often  require  the  re-shap- 
ing of  ready-made  teeth  by  grinding,  and  the  original  form 
should  never  be  preserved  at  the  sacrifice  of  utility  and  appear- 
ance. 

To  Secure  Harmony  of  Color  in  the  use  of  manufactured 
teeth  as  found  in  dental  depots  is  not  always  practicable. 
There  are  often  conditions  of  the  natural  organs  associated  with 
decay  and  organic  discolorations  which  it  is  impossible  to  match 
with  porcelain  teeth  provided  by  manufacturers  for  general 
purposes.  Such  needs  of  the  practitioner  can  only  be  ade- 
quately met  by  selecting  the  teeth  and  having  them  stained 
before  baking  at  the  dental  depot. 

Grinding  the  Teeth. — A  greater  or  less  change  in  the  form 
of  porcelain  teeth  will  be  required,  in  nearly  all  cases,  in  fitting 
them  to  the  vacuities  in  the  jaw  ;  and  this  is  more  particularly 
so  in  those  cases  requiring  the  use  of  gum  teeth.  This  altera- 
tion of  form  is  effected  by  grinding  away  portions  of  the  tooth 
upon  an  emery  or  carborundum-wheel  attached  to  the  dental 
lathe.  (Fig.  492.)  If  the  edentulous  portions  of  the  ridge  have 
suffered  but  little  change  of  form  by  absorption,  as  where  the 
teeth  have  been  recently  extracted,  and  plain  teeth  (those  repre- 
senting only  the  crowns  of  the  natural  organs)  are  used,  the 
posterior  portions  of  the  base  of  the  latter  resting  upon  the 
margins  of  the  plate  will  only  require  to  be  conformed  to  the 
irregularities  on  the  surface  of  the  base-plate,  grinding  suffi- 
ciently to  give  them  the  proper  length  and  relative  position, 
while  their  anterior  cervical  portion  is  permitted  to  overlap  the 
edge  of  the  plate  and  rest  directly  upon  the  gum  in  front  on  a  line 


SELECTING    AND    ARRANGING    THE    TEETH. 


419 


with  the  adjoining  teeth.  When,  however,  a  considerable  con- 
cavity exists  in  the  ridge  and  external  border,  and  single  gum 
teeth  are  employed  to  restore  the  customary  fulness  and 
contour  of  the  parts,  the  gum  portion  of  the  tooth  should  be 
ground    away  on   its   posterior  face   sufficiently  to   restore   the 

Fig.  492. 


circle  of  the  gum  on  the  external  border  of  the  alveolus,  and 
from  the  base  of  the  tooth  where  it  rests  upon  the  plate,  to 
admit  of  a  proper  relative  position  of  the  artificial  crown  ;  while 
those  portions  of  the  porcelain  gum  terminating  at  and  adjoin- 
ing the  remaining  teeth,  next  the  spaces,  should  be  formed  with 


420  MECHANICAL    DENTISTRY. 

a  thin,  retreating  edge,  where  it  laps  upon  the  natural  gum, 
giving  to  the  parts,  when  the  substitute  is  adjusted  to  the  mouth, 
the  appearance  of  an  unbroken  denture  and  a  continuous  gum. 
When  the  space  to  be  supplied  requires  a  series  of  two  or  more 
single  gum  teeth,  the  latter  should  be  united  to  each  other  with 
the  greatest  care  and  exactness  by  grinding  the  proximate  edges 
of  the  gum  portions  until  the  coaptation  is  such  as  to  render  the 
seams  imperceptible  in  the  mouth.  In  adjusting  the  porcelain 
teeth  to  the  plate,  the  base  of  each  tooth  should  be  ground  to 
rest  as  directly  and  uniformly  on  the  plate  as  possible;  for  if 
thrown,  in  any  degree,  from  the  plate,  the  whole  strain  in  mas- 
tication will  come  upon  the  platinum  rivets,  and,  in  a  compara- 
tively short  time,  the  latter  will  either  be  entirely  worn  or  cut 
off,  or  the  artificial  crown  will  be  fractured  on  a  line  with  the 
pins. 

Antagonizing    Partial    Dentures. — In   antagonizing   partial 
sets  of  teeth,  the  indications  pointed  out  by  the  customary  clos- 
ure of  the  natural  organs   should  be  followed  as   nearly  as  the 
form  and  position  of  the  opposing  teeth  will  permit.     A  changed 
or  abnormal   relation  of  the  teeth   of  both  jaws,  however,  fre- 
quently renders  it  difficult  to  effect  a  satisfactory  adjustment  of 
the  teeth  of  replacement.     If,  in  the  case  of  the  bicuspids,  for 
example,   one  or  more  teeth  in  the  under   jaw   project  into  a 
vacuity  above  to  the  extent  of  one-third  or  more  of  its  depth,  a 
direct  closure  of  the  substituted  organs  upon  these,  in  the  ordi- 
nary manner,  would  be  impracticable  without  a  corresponding 
shortening  of  the  porcelain  teeth,  enforcing,  in  such   cases,  an 
inharmonious  arrangement,  entirely    inconsistent  with  the   just 
requirements   of  the  case.     The    difficulty  cited,   or  any  of  the 
various  modifications  of  it,  may  be  overcome  wholly,  or  in  part, 
in  one  of  two  or  three  ways.     If  the  teeth  encroaching  upon  the 
opposite  space  are  very  loose,  as   is   frequently  the  case  with 
those  that  have  become  elongated  from  the  long-continued  want 
of  an  adequate  opposing  force,  or  are  hopelessly  carious  or  other- 
wise diseased,  they  should  be  at  once  removed.     If  they  remain 
firm  and  sound,  and  stand  slightly  within  the  circle  of  the  teeth 
of  the  opposite   jaw,  or  if  they  have   somewhat  of  an   inward 
inclination  in  the  arch,  the  vacuity  opposite  may  be   filled  with 


SELECTING    AND    ARRANGING    THE    TEETH.  42 1 

non-masticating  teeth,  as  a  canine,  on  the  Hngual  side  of  which 
an  antagonizing  cusp  of  gold  may  be  constructed,  allowing  the 
point  of  the  cuspid  to  lap  over  the  labial  face  of  the  encroaching 
tooth  or  teeth  ;  or  a  bicuspid,  manufactured  for  the  purpose,  with 
the  inner  cusp  near  the  base  of  the  tooth,  may  be  used  instead. 
Additional  room  may  be  provided  in  such  cases  for  the  overlap- 
ping portion  by  grinding  away  from  a  corresponding  point  on 
the  opposing  tooth.  If,  however,  taking  the  most  impracticable 
case,  the  intruding  teeth  are  sound  and  firm,  and  stand  verti- 
cally in  the  arch,  closing  between  the  opposing  teeth  on  a  line 
with,  or  somewhat  outside  of,  the  outer  circle  of  the  latter  (the 
elongation  of  such  teeth  being  rather  relative  than  absolute,  as 
where  it  results  from  a  mechanical  wearing  away  of  the  remaining 
antagonizing  teeth  and  a  corresponding  approximation  of  the 
jaws),  the  practitioner  will  be  compelled  either  to  submit  to  a  mal- 
arrangement  of  the  teeth  of  replacement  by  grinding  away  suffi- 
ciently from  their  grinding  surfaces  to  permit  an  unobstructed 
closure  of  the  natural  organs,  or  if  the  remaining  teeth  are  few 
and  poor  in  structure,  extract  them,  and  insert  a  full  denture. 

In  view  of  the  difficulties  which  so  frequently  present  them- 
selves in  connection  with  the  arrangement  of  artificial  teeth  in 
partial  cases,  it  may  not  be  amiss  to  observe  that,  however  essen- 
tial to  the  natural  and  agreeable  expression  of  the  individual  an 
exact  and  harmonious  arrangement  of  the  teeth  of  replacement 
may  be,  this  requirement  should,  in  some  degree,  be  disregarded 
whenever  the  necessities  of  the  patient,  in  respect  of  the  com- 
fort and  utility  of  the  appliance  or  the  safety  of  the  natural  organs, 
demand  it ; — to  what  extent  appearances  should  be  sacrificed  to 
these  considerations  will  depend  upon  the  peculiar  exigencies  of 
the  case,  and  cannot,  iherefore,  be  specifically  stated.  On  the 
other  hand,  it  may  be  observed  that,  if  a  sufficient  number  of 
the  natural  teeth  are  remaining  in  both  jaws  to  enable  the  patient 
to  perform,  with  tolerable  efficiency,  the  act  of  mastication,  the 
mere  utility  of  the  substitute  in  regard  to  the  performance  of 
this  function  may  be  partly  or  wholly  disregarded  whenever 
there  is  sufficient  reason  to  apprehend  that  the  substituted 
organs  cannot  be  antagonized  with  a  view  to  the  comminution 
of  food  without  endangering  the   permanency    and    usefulness 


422 


MECHANICAL    DENTISTRY. 


of  the   appliance  by  necessitating  the  application   of  forces  un- 
favorably directed. 

Investing. — Having  arranged  and  antagonized  the  teeth  as 
accurately  as  possible  on  the  plaster  model,  the  piece  should  be 
placed  in  the  mouth  to  detect  and  remedy  any  faultiness  that 
may  be  found  to  exist  either  in  the  adaptation,  position,  or 
antagonism  of  the  artificial  teeth.  It  is  then  removed  and 
embedded  in  a  mixture  of  plaster,  sand,  and  asbestos,  in  the  pro- 
portion of  about  two  parts  of  the  former  and  one  part  each  of 
the  latter.  The  body  of  the  investment  may  be  surrounded 
by  a  copper  or  sheet-iron  band  to  prevent  it  from  break- 
ing away  whilst  adjusting  the  stays  or  linings  to  the  teeth.     All 

Fig.  493. 


parts  of  the  plate  and  teeth,  except  the  lingual  side  of  the  former 
and  the  backs  of  the  latter,  should  be  encased  to  the  depth  of 
half  an  inch  or  more,  and  when  the  latter  is  sufficiently  hard  all 
traces  of  wax  from  the  inside  should  be  carefully  detached  with 
suitable  instruments. 

Manner  of  Backing  the  Teeth. — The  piece  is  now  ready  for 
the  adjustment  of  stays  or  backings,  which,  when  permanently 
united  by  soldering  to  the  base  and  teeth,  are  designed  to  sustain 
the  latter  in  position.  These  supports  are  formed  from  plate 
somewhat  thicker  than  that  used  for  the  base,  a  heavier  and 
stronger  stay  being  necessary  when  they  are  not  united  laterally, 
as  when  plate  teeth  are  used.  If,  however,  single  gum  or  block 
teeth  are  employed,  and  the  stays  are  joined,  forming  a  continu- 
ous band,  plate  one-half  thicker  than  that  used  for  the  base  will. 


SELECTING    AND    ARRANGING    THE    TEETH. 


4- 


ordinarily,  impart  adequate  security  to  the  attachment.  A  plain 
strip,  corresponding  in  width  with  the  tooth  to  be  lined,  is  cut, 
and  the  end  resting  on  the  main  plate  conformed  accurately  with 
the  file  to  the  irregularities  on  the  surface  of  the  latter,  and  in 
such  a  manner  as  to  permit  the  strip  to  take  the  direction  of  the 
tooth.  The  general  form  of  the  stay  may,  in  the  first  place,  be 
obtained  by  cutting  a  strip  from  a  piece  of  gold  with  a  pair  of 
plate  forceps  (Fig.  493).     The  points  upon  the  stay  to  be  pierced 

Fig.  494. 


for  the  admission  of  the  platinum  pins  may  be  ascertained  by 
coating  the  surface  of  the  former  with  wax  softened  in  the  flame 
of  a  spirit-lamp,  and  pressing  it  first  against  the  lower  pin,  the 
point  of  which  w'ill  be  indicated  b}'  an  indentation  of  the  wax.  The 
backing  is  then  perforated  at  this  point  with  a  plate  punch,  two 
forms  of  which  are  exhibited  in  Fig.  494,  one  armed  with  a 
tongue,  which,  when  the  plate  is  pierced,  forces  the  latter  from 
the  punch.  The  strip  is  then  reapplied  to  the  upper  pin,  and  the 
second  hole  obtained  in  like  manner  as  the  first.  Instead  of 
using  wax,  the  ends  of  the  rivets  may  be  stained  with  some  pig- 
ment, which  will  show  the  points  to  be  pierced  in  the  lining. 


424  MECHANICAL    DENTISTRY. 

The  stay  should  be  adapted  accurately  to  the  face  of  the  tooth  ,; 
it  is  then  cut  to  the  proper  length,  reaching  nearly  or  quite  to  the 
point  of  the  tooth,  and  shaped  with  a  file  to  the  general  form 
of  the  crown.  When  the  stays  are  to  be  united  they  should 
be  formed  with  a  shoulder  at  a  point  corresponding  with  the 
neck  of  the  tooth,  and  the  proximate  edges  below  united  closely 
by  square  edges,  or  the  latter  may  be  beveled  and  made  to  lap 
upon  each  other.  The  process  of  soldering  will  be  greatly 
facilitated  and  the  piece  will  be  more  easily  and  artistically 
finished  by  securing,  in  the  first  instance,  a  perfect  coaptation  of 
all  the  parts  which  are  ultimately  to  be  united.  The  sides  of  the 
holes  in  the  stays  facing  the  plate  should  now  be  enlarged  or 
countersunk  with  a  spear-shaped  or  conical  bur  drill,  and  when 
applied  to  the  teeth  the  projecting  ends  of  the  platinum  pins  are 
cut  off  even  with  the  backings  and  then  split  and  spread  apart 
with  a  small  chisel-shaped  instrument ;  a  head  will  thus  be 
formed  to  the  rivets  when  solder  is  fused  upon  them,  which  will 
prevent  them  from  drawing  from  the  linings. 

The  Soldering  Process. — All  the  lines  of  union  between  the 
several  pieces  should  next  be  well  scraped,  exposing  a  clean, 
bright,  metallic  surface  to  the  solder ;  the  seams  are  then  coated 
with  borax,  ground,  or  rubbed  in  clean,  soft  water  to  about  the 
consistency  of  cream  ;*  after  which  small  pieces  of  solder  are 
placed  along  the  joints  and  over  the  points  of  the  platinum  pins. 
The  piece  thus  prepared  is  now  placed  in  the  furnace  or  ordinary 
fireplace  in  order  to  heat  the  entire  mass  preparatory  to  solder- 
ing. The  fuel  most  proper  for  this  purpose  is  charcoal,  either 
alone  or  combined  with  coke,  the  latter  being  preferable  for  the 
reason  that  charcoal  alone  is  more  quickly  consumed,  and  burn- 
ing away  more  rapidly  underneath  the  piece  is  liable  to  drop  to 
the  bottom  of  the  furnace.  The  fuel  should  be  broken  into 
small  pieces  and  built  up  around  the  borders  of  the  investient  in 
order  that  all  parts  of  the  latter  may  be  uniformly  heated.  The 
heating  process  should  be  conducted  gradually,  for  if  the  piece 

*  Slate  is  often  used  for  this  purpose,  but  is  unfit,  as,  in  rubbing  the  borax,  loosened 
particles  of  the  former  become  mixed  with  the  latter  and  impede  the  flow  of  the 
solder,  and  becoming  entangled  render  it  unclean  and  porous.  Ground  glass  or  a 
porcelain  slab  is  the  best  for  the  purpose. 


INVESTING,    ADJUSTING    STAYS,    SOLDERING,    ETC.  425 

to  be  soldered  is  subjected  suddenly  to  a  high  heat,  the  plaster 
will  be  displaced  by  the  too  rapid  evolution  of  vapor,  and  the 
integrity  of  the  porcelain  teeth  will  be  endangered.  The  piece 
may  be  allowed  to  remain  in  the  fire  until  the  plate  acquires  a 
visible  red  heat,  when  it  should  be  removed,  placed  on  a  suitable 
holder,  and  the  solder  fused  with  the  blowpipe.  A  broad,  spread- 
ing flame  should  first  be  thrown  over  the  entire  surface  of  the 
plate  and  border  of  the  plaster  until  the  temperature  of  the 
entire  mass  is  nearly  that  required  to  fuse  the  solder,  and  which 
is  indicated  by  the  latter  settling  and  contracting  upon  itself; 
the  flame  may  then  be  concentrated  upon  a  particular  point,  as 
at  the  heel  of  the  plate  on  one  side,  passing  round  from  tooth  to 
tooth  until  all  the  parts  are  completely  united  and  the  solder  is 
well  and  uniformly  diffused. 

Having  united  the  teeth  to  the  plate,  the  piece  may  be 
allowed  to  cool  gradually,  or  it  may  be  plunged  after  the  lapse  of 
a  few  minutes  into  boiling  water  without  risk  of  injury  to  the 
teeth.  When  cool,  the  plaster  is  removed  and  the  plate  placed 
in  the  acid  batJi  (a  solution  of  equal  parts  of  sulphuric  acid  and 
water),  where  it  may  be  allowed  to  remain  until  the  discoloration 
of  the  plate  and  the-  remains  of  the  vitrified  borax,  incident  to 
the  soldering,  are  removed,  or  it  may  be  put  into  a  small  copper 
vessel,  partly  filled  with  the  same  solution,  and  boiled  for  a  few 
minutes.  After  removing,  the  plate  from  the  acid,  it  should  be 
boiled  for  five  or  ten  minutes  in  a  solution  of  chlorid  of  soda  or 
common  salt  and  water  to  remove  thoroughly  all  traces  of  the 
former. 

The  Finishing  Process. — Superfluous  portions  of  solder  are 
now  to  be  removed,  and  this  at  first  may  be  more  quickly 
accomplished  by  the  use  of  burs  of  various  forms  and  sizes 
attached  to  the  dental  engine.  After  the  rougher  and  more 
redundant  parts  are  thus  cut  away,  any  remaining  irregularities 
upon  the  surface  may  be  further  reduced  with  properly  formed 
stones  and  disks.  Then  with  a  rapidly  revolving  brush  attached 
to  a  foot-lathe,  the  final  polish  or  luster  may  be  imparted  by  the 
use,  first,  of  Spanish  whiting,  or  prepared  chalk,  and  then  rouge 
mixed  with  water  or  alcohol. 

In  the  final  adjustment  of  the  finished  piece  to  the  mouth,  and 


426  MECHANICAL    DENTISTRY. 

after  any  additional  change  in  the  form  of  the  teeth  necessary 
to  secure  the  most  perfect  antagonism  has  been  made,  the 
patient  should,  in  all  cases  of  partial  dentures,  receive  explicit 
directions  in  regard  to  the  general  care  and  management  of  the 
appliance  and  the  remaining  natural  teeth.  Ordinarily,  there 
will  be  but  little  difficulty  experienced  by  the  patient  in  the 
immediate  and  successful  use  of  a  substitute  supported  in  the 
mouth  by  clasps,  or  any  equivalent  means,  but  in  the  case  of 
atmospheric-pressure  plates,  the  patient  should  be  candidly 
advised  of  the  probable  want  of  stability  incident  to  the  first 
use  of  the  appliance,  and  the  consequent  annoyance  which  in 
many  cases  follows  its  occasional  displacement  in  mastication 
until  such  time  as  the  adaptation  of  the  several  parts  to  each 
other  are  perfected,  and  the  patient  has  acquired  a  habit  of  con- 
trolling and  directing  the  forces  applied  to  the  substitute.  The 
time  necessary  to  accomplish  these  results  will  depend  much 
upon  the  form  and  condition  of  the  mouth,  a  favorable  or 
unfavorable  antagonism,  the  adaptation  of  the  plate,  and  the 
aptitude  and  temper  of  the  patient.  It  will  be  prudent  and  but 
just  to  the  patient  to  state  that  the  complete  utility  of  an  appli- 
ance sustained  by  atmospheric  pressure  will  not,  probably,  be 
realized  in  less  time  than  from  one  to  two  weeks,  and  this  esti- 
mate of  time,  in  a  majority  of  cases,  will  be  fully  justified  by 
experience  in  the  cases  under  consideration. 

The  importance  of  thorough  and  absolute  cleanliness  of  the 
substitute  and  remaining  natural  teeth,  and  the  reasons  therefor, 
should  be  clearly  stated;  and  the  comfort,  utility,  and  durability 
of  the  artificial  fixture,  as  well  as  the  safety  of  all  the  remaining 
natural  organs,  will  depend,  in  a  great  measure,  upon  the  fidelity 
of  the  patient  with  respect  to  the  observance  of  these  injunc- 
tions. In  those  cases  especially  where  clasps  are  used,  the  sub- 
stitute should  invariably  be  removed  after  each  meal  and 
cleansed,  while  the  teeth  clasped  should,  at  the  same  time,  be 
freed  from  deposits  of  food  or  other  foreign  substances  with  a 
brush,  and  other  means  usually  recommended  for  the  purpose. 


CHAPTER  IX. 

ENTIRE  DENTURES. 

Before  proceeding  to  describe  in  detail  the  mechanical  pro- 
cesses or  manipulations  concerned  in  the  construction  of  entire 
dentures,  unnecessary  repetition  will  hereafter  be  avoided  by 
first  considering  in  this  place  certain  underlying  principles  and 
fundamental  requirements  which  are  common  to  all  the  various 
distinct  methods  of  replacement  in  edentulous  cases.  This 
preliminary  treatment  of  the  subject  ma}^  be  comprehended 
under  two  general  heads:  (i)  a  consideration  of  the  principles 
and  attendant  phenomena  involved  in  the  application  of  the 
forces  commonly  utilized  as  a  means  of  attachment;  and  (2) 
esthetic  requirements  in  the  selection  and  arrangement  of  the 
teeth  of  replacement.  There  are  two  forces  in  nature  utilized 
in  the  retention  of  entire  dentures,  notably  in  upper  cases, — 
Atmospheric  Pressure  and  Adlicsion.  We  shall  consider,  first, 
some  of  the  attributes  and  phenomena  characteristic  of  these 
forces,  and  then  endeavor  to  make  some  practical  application  of 
them  in  elucidation  of  the  subject  in  hand. 

Adhesion  maybe  defined  as  the  force  by  which  the  particles 
of  different  bodies  stick  together,  in  contradistinction  to  cohe- 
sion, which  is  the  force  that  holds  the  molecules  of  the  same 
body  together.  There  are  a  number  of  different  kinds  of  adhe- 
sion, but  our  present  purpose  only  contemplates  those  which 
relate  to  the  adhesion  of  solids  to  solids,  and  fluids  to  solids. 

The  adhesion  of  solids  to  solids  is  illustrated  by  pressing 
together  two  plates  of  glass  or  metal  having  perfect  occluding 
surfaces,  when  they  will  be  found  to  adhere  with  force  enough 
to  support  not  only  the  lower  plate,  but  some  additional  weight. 
Very  delicate  tests  have  been  made  by  which  the  adhesive  force 
is  accurately  measured.  An  important  practical  fact,  in  this 
connection,  has  been  well  established,  which  has  a  direct  bear- 
ing on  the  subject  we  are  considering,  namely,  that  the  tenacity 

427 


428  MECHANICAL    DENTISTRY, 

with  which  such  plates  adhere  to  each  other  is  not  in  any  man- 
ner due  to,  but  wholly  independent  of,  any  force  exerted  by  the 
pressure  of  the  atmosphere,  as  was  supposed  by  some  of  the 
earlier  experimenters.  The  fact  alluded  to  was  conclusively 
proven  by  suspending  the  plates,  the  lower  one  of  which  was 
weighted,  in  the  vacuum  of  an  air-pump,  in  which  case  the 
plates  still  remained  adherent.  Examples  of  this  adhesive 
force  as  affecting  solids  might  be  almost  indefinitely  multiplied. 

The  force  of  adhesion  of  solids  to  liquids  is  not  less  pro- 
nounced. When  a  polished  plate  is  suspended  on  a  delicately 
constructed  balance,  and  brought  carefully  down  on  the  surface 
of  a  liquid,  completely  excluding  the  air,  adhesion  will  take 
place,  the  force  of  which  will  be  modified  by  the  kind  of  liquid 
in  contact  with  the  plate.  It  has  been  ascertained  by  careful 
experiment  that  the  adhesive  force  of  a  polished  plate  of  agate, 
one  inch  in  diameter,  in  contact  with  water,  is  25  grains;  sul- 
phuric acid,  29  ;  hydrochloric  acid,  25  ;  solution  of  saltpetre,  25  ; 
of  lime,  21;  almond  oil,  16;  petroleum,  16;  turpentine  and 
alcohol,  15;  ether,  10.  Where,  as  often  happens,  drops  of  the 
liquid  adhere  to  the  plate  when  separated,  it  proves  that  the 
adhesion  of  the  liquid  to  the  solid  is  stronger  than  the  cohesion 
of  the  liquid  itself,  and  that  the  numbers  obtained  in  these 
experiments  express  rather  the  cohesion  of  particles  of  the  liquid 
which  were  separated  by  the  weight,  than  the  adhesion  of  the 
plate  to  the  liquid.  As  in  the  case  of  adhesion  of  solids  to 
solids,  it  was  formerly  claimed  by  some  that  adhesion  in  these 
cases  was  due  to  atmospheric  pressure,  but  that  was  disproved 
in  the  same  manner  as  the  other.  Perfect  exclusion  of  air  is 
essential  to  the  operation  of  this  force,  a  suggestive  fact  in  con- 
nection with  the  adaptation  and  retention  of  entire  dentures. 

Atmospheric  Pressure  is  that  force  exerted  by  the  air  by 
reason  of  its  gravity,  one  of  its  mechanical  properties  being 
iveight,  which  renders  it  amenable  to  the  same  law  of  attraction 
that  affects  all  other  bodies  similarly  endowed.  It  exerts  a 
pressure  not  only  downward,  but,  according  to  the  law  of  fluids, 
sideways,  upward,  etc.,  as  by  the  mobility  of  fluid  particles  any 
pressure  is  transmitted  in  all  directions.  Superadded  to  gravity 
is  its  elastic  force,  a  property  which,  like   all  gaseous  bodies,  it 


ENTIRE    DENTURES.  429 

possesses  in  a  remarkable  degree.  This  property  is  familiarly 
demonstrated  by  filling  a  bladder  with  air  and  exposing  it  to 
rarefied  air  at  a  great  height.  The  external  pressure  of  the 
atmosphere  at  such  an  altitude  being  diminished,  the  air  within 
tends  to  expand  to  the  same  degree  of  rarity  as  that  without,  and 
with  such  force  as  to  burst  the  bladder.  The  partial  displace- 
ment of  air  by  compression  within  a  diving-bell  by  the  pressure 
of  water  at  a  low  depth,  and  the  forcible  expulsion  of  the  intrud- 
ing water  as  the  bell  is  brought  to  the  surface,  not  only  illustrates 
its  elasticity,  but  its  impenetrability  also,  or  its  property  of  pre- 
venting another  body  from  occupying  the  space  where  it  is. 
There  are  many  other  examples  of  the  pressure  of  the  atmos- 
phere and  the  force  exerted  by  virtue  of  its  elastic  property,  but 
those  of  most  interest  and  consequence  to  the  prosthetic  special- 
ist relate  to  their  effects  on  the  human  organism.  It  is  estimated 
that  the  force  exerted  by  the  pressure  of  the  atmosphere  on  the 
body  of  a  medium-sized  man  must  be  about  fifteen  tons,  a  force 
sufficient  to  crush  and  destroy  him  if  applied  only  to  the  external 
portions  of  the  body.  Such  pressure,  hovvever,  is  neutralized 
and  rendered  harmless  by  counter-pressure  from  within  ;  a  result 
due  to  the  elasticity  of  the  air,  which  exerts  a  force  everywhere 
and  in  all  directions  alike,  from  the  external  parts  inwardly,  and 
from  those  within  outwardly.  The  tendency  in  nature  every- 
where is  toward  the  establishment  of  an  equilibrium  of  atmos- 
pheric pressure,  and  when  these  balanced  forces  are  disturbed, 
unusual  and  characteristic  phenomena  follow.  If,  as  in  the  case 
of  "  cupping,"  the  external  pressure  of  the  atmosphere  is  removed 
by  the  formation  of  a  vacuum,  the  elastic  force  of  the  air  opera- 
ting from  within,  and  meeting  no  counter-force  at  the  point 
cupped,  will,  by  virtue  of  its  inherent  elastic  energy,  force  the  soft 
tissues  into  the  body  of  the  cup  as  the  result  of  this  tendency  to  an 
equilibrium.  The  latter  occurs  as  soon  as  the  unoccupied  space 
forming  the  vacuum  is  filled  with  the  tissues,  when,  the 
accustomed  balance  of  forces  being  restored,  the  cup  will  loosen 
and  fall  off.  If  the  disturbance  of  the  equilibrium  of  forces 
acting  from  without  and  within  is  general,  as  in  the  case  of  an 
aeronaut  in  a  balloon  at  great  heights,  the  result  of  this  tendency 
may,  and  often   has,  put  life  in   jeopardy  by  expansion    of    the 


430  MECHANICAL    DENTISTRY. 

internal  organs.  On  the  contrary,  the  body  exposed  to  greatly 
increased  external  pressure  of  the  air,  as  when  the  latter  is  con- 
densed in  the  diving-bell  at  low  depths,  or  in  caissons  employed 
in  forming  a  foundation  of  subaqueous  structures,  the  results  may 
be  equally  harmful  or  fatal  by  compression  of  the  internal 
organs. 

The  Application  of  Atmospheric  Pressure  and  Adhesion 
in  the  Retention  of  Artificial  Dentures.— Let  us  now  make 
some  brief  application  of  the  above  well-established  facts  in 
explanation  of  the  manner  in  which  atmospheric  pressure  and 
adhesion  act  as  forces  in  the  retention  of  so-called  "  Atmo- 
spheric-Pressure Plates,"  and  the  phenomena  and  results  of  such 
action. 

This  discussion  may  be  premised  with  the  statement  of  the 
general  proposition  that,  in  the  case  of  entire  dentures,  retention 
of  the  plate  in  place  by  atmospheric  pressure  presupposes  a 
vacuum  obtained  by  exhaustion  of  the  air  from  a  cavity,  of  what- 
ever form,  located  somewhere  between  the  plate  and  the  mucous 
surfaces  on  which  the  latter  rests,  and  that  such  cavity  implies 
space.  Whenever,  therefore,  a  dental  appliance  of  the  kind 
under  consideration  is  in  uniform  contact  at  all  points  with  the 
parts  in  the  mouth,  it  is  manifestly  improper  to  speak  of  it  as 
being  held  in  place  by  atmospheric  pressure,  or  to  designate  it 
as  an  "  atmospheric-pressure  plate."  Uniform  contact  implies 
perfect  continuity  between  the  plate  and  the  parts  on  which  it 
rests,  and  this  necessarily  precludes  the  idea  of  space,  and  with- 
out space  a  vacuum  is  impossible,  and  in  the  absence  of  the 
latter,  the  atmosphere,  as  we  shall  endeavor  to  show,  is  wholly 
inoperative  as  a  retaining  force.  To  comprehend  the  matter 
intelligently,  we  must  not  lose  sight  of  the  important  central 
fact  that  the  atmosphere,  in  its  undisturbed  condition,  exerts 
an  equal  pressure  in  all  directions,  a  property  largely  due  to  its 
elasticity,  and  that  in  obedience  to  this  law,  in  its  operation  upon 
the  human  organism,  the  force  exerted  from  without  inward  is 
exactly  counterbalanced  by  the  same  force  acting  from  within 
outward,  thus  establishing  an  equilibrium  of  the  counteracting 
forces,  and  a  consequent  neutralizing  of  pressure  at  the  surface. 
This  equalized   force   is   an  essential   condition  of  human  well- 


ENTIRE    DENTURES.  43  I 

being  and  of  human  life,  as  has  been  heretofore  stated  and 
demonstrated  by  exam.ples.  The  absurdity,  therefore,  of 
attributing  the  retention  of  substitutes,  adapted  in  this  manner 
to  the  mouth,  to  the  pressure  of  the  atmosphere  is  apparent. 
There  can  be  no  reasonable  question  but  that  substitutes  so 
applied  are  held  in  situ  by  that  force  manifesting  itself  in 
Adhesion.  In  all  cases  where  the  plate  or  other  base  is  accu- 
rately adapted  to  the  entire  mucous  surfaces,  and  the  air 
thoroughly  excluded,  the  essential  conditions  favoring  its  reten- 
tion by  adhesion  is  secured,  namely,  perfect  contact  of  a  solid 
with  the  fluids  with  which  the  mucous  surfaces  are  constantly 
bathed. 

Let  us  now  consider,  as'  briefly  as  possible,  the  manner  in  which 
air-pressure  acts  as  a  retaining  force  when  applied  to  cavity- 
plates,  and  in  the  same  connection  some  of  the  phenomena 
resulting  from  such  action. 

When  a  plate,  provided  with  a  cavity  or  chamber,  is  applied 
to  the  mouth,  two  concurrent  phenomena  are  observed — the 
immediate  and  forcible  attachment  of  the  plate  to  the  mucous 
surfaces,  and  the  obtrusion  of  the  soft  tissues  into  the  space  from 
which  the  air  has  been  exhausted.  The  first  is  due  to  the 
external  pressure  of  the  atmosphere,  the  latter  to  the  same  force 
acting  from  within.  Here,  again,  it  is  essential  to  remember  the 
fundamental  fact  that  atmospheric  pressure  acts  equally  in  all 
directions.  In  the  case  of  the  human  body,  as  before  stated,  the 
pressure  of  the  air  from  without  inwardly  is  exactly  counter- 
balanced by  the  pressure  of  the  atmosphere  within  outwardly, 
establishing  in  this  manner  an  exact  equilibrium  of  forces,  the 
one  neutralizing  the  other  at  the  surface.  The  phenomena  to 
which  attention  has  been  called,  in  the  case  of  an  applied  cavity- 
plate,  are  the  result  of  a  disturbance  of  these  ordinarily  balanced 
forces.  When  a  vacuum,  partial  or  complete,  is  formed  by 
exhaustion  of  air  from  the  chamber,  the  external  pressure  of 
the  air  meeting  with  a  diminished  counter-resistance  from 
within,  by  reason  of  the  vacuum,  forces  the  plate  against  the 
parts,  while  at  the  same  time  the  atmospheric  pressure  acting 
from  within  outwardly,  meeting  with  a  like  diminished  resistance 
at  the  surface  embraced  within  the  limits  of  the  chamber,  forces 


432  MECHANICAL    DENTISTRY. 

the  soft  tissues  into  the  chamber.  Thus  we  find  displayed  the 
universal  tendency  to  an  equilibrium  of  atmospheric  pressure, 
and  a  practical  illustration  of  nature's  proverbial  abhorrence  of  a 
vacuum. 

It  is  not  probable  that  a  perfect  vacuum  is  ever  secured  by  the 
means  ordinarily  employed  by  the  patient,  unless,  perhaps,  in 
the  case  of  very  shallow  cavities.  The  moment  any  portion  of 
the  contained  air  is  exhausted,  there  is  instant  and  forcible  pres- 
sure of  the  plate  upon  the  soft  tissues  immediately  surrounding 
the  chamber,  acting  as  an  effectual  mechanical  impediment  to 
farther  egress  of  air.  The  power  to  exhaust  is  therefore  self- 
limited,  and  a  partial  vacuum  only  the  result.  Sooner  or  later, 
in  a  large  percentage  of  cases,  even  this  limited  power  is 
rendered  inadequate  to  secure  any  degree  of  exhaustion  by  the 
intrusion  of  tissues  which,  by  long-continued  and  unrelieved 
pressure,  become  in  time  permanently  hypertrophied. 

The  completeness  with  which  the  chamber  may  become  filled 
with  soft  tissues  will  depend  partly  upon  the  form  of  the  cavity, 
and  partly  upon  the  abundance  and  mobility  of  the  tissues.  If 
the  cavity  is  constructed  with  vertical  walls  and  sharply-defined 
margins,  the  latter,  by  becoming  quickly  imbedded,  will  act  as  a 
mechanical  obstruction  to  any  ready,  sliding  movement  of  the 
tissues  into  the  chamber.  Plates  so  constructed  adhere  with 
greater  tenacity  and  more  persistency,  especially  when  the  parts 
embraced  are  rigid  and  immobile ;  but  it  is  at  the  cost  of  the 
maximum  of  injury  which  cavity  plates  are  capable  of  inflicting, 
and  which  is  often,  in  extreme  cases,  characterized  by  rupture 
of  the  superficial  vessels,  wounding  of  the  mucous  membrane, 
and  in  active  inflammatory  conditions  which  not  infrequently 
involve  the  adjacent  tissues.  More  ready  entrance  of  the  tissues 
into  the  chamber  occurs  where  the  edges  of  the  latter  are 
rounded  and  the  walls  slope  toward  the  center,  as  in  the  case  of 
those  that  are  swaged,  but  this  form  is  at  the  expense  of  the 
retaining  force,  since  atmospheric  pressure  from  without  is 
always  diminished  in  proportion  as  the  cavity  becomes  filled  in 
with  the  tissues,  and  ceases  entirely  when  a  vacuum  no  longer 
exists.  The  facility  with  which  the  chamber  will  become  occu- 
pied is  greatly  increased  when  the  soft   tissues  are  in  excess. 


ENTIRE    DENTURES.  433 

their  softness  and  mobility  offering  but  a  feeble  resistance  to  the 
atmospheric  pressure  from  within,  in  which  case  the  cavity  soon 
becomes  partly  or  wholly  occupied  by  them,  and  what  retaining 
force  was  originally  secured  by  atmospheric  pressure  will,  in  a 
comparatively  short  time,  become  greatly  impaired  or  wholly 
inoperative. 

In  addition  to  the  force  acting  from  within,  tending  to  weaken 
the  attachment  of  a  cavity  plate  by  filling  in  the  chamber  with 
soft  tissues,  there  is  another  force,  acting  mechanically,  which 
contributes  in  no  inconsiderable  degree  to  the  same  result.  On 
exhaustion  of  the  air  from  the  chamber,  the  plate,  being  pressed 
with  considerable  force  against  the  mucous  surfaces,  will  exert  a 
corresponding  pressure  upon  the  tissues  immediately  surround- 
ing the  chamber,  the  mobility  of  which  admits  of  more  or  less 
displacement,  and  as  this  always  occurs  in  the  direction  of  the 
least  resistance,  they  readily  enter  the  cavity. 

When  it  is  remembered  how  ina^dequate  and  transitory  are 
the  uses  of  so-called  "air-chambers,"  and  how  capable,  under 
ordinary  circumstances,  they  are  of  inflicting  serious  and  perma- 
nent injury  upon  the  delicate  tissues  of  the  mouth,  there  would 
seem  to  be  no  sufficient  reason  or  justification  for  their  employ- 
ment, except  possibly  in  rare  and  exceptional  cases.  Experience 
has  mnply  demonstrated  that  equally  secure  and  mucJi  more  endur- 
ing attachment  of  the  substitute  may  be  obtained  in  the  utilizatio7i  of 
adhesive  force  alone — a  means  of  retention  wholly  exempt  from 
the  harmful  consequences  that  too  often  follow  the  application 
of  atmospheric  pressure  consequent  on  the  formation  of  a 
vacuum. 

There  are,  however,  many  cases  where  spaces  or  cavities  may 
be  employed  to  advantage  for  the  purpose  of  securing,  through 
the  temporary  pressure  of  the  atmosphere,  increased  stability  of 
a  dental  appliance  subjected  to  the  forces  applied  in  mastication. 
There  are  associated  conditions  of  the  mouth  which,  in  their 
normal  and  undisturbed  relation  to  each  other,  prevent,  to  some 
extent,  a  uniform  or  equalized  bearing  of  the  substitute  upon 
the  parts  to  which  it  is  applied.  These  conditions  relate  to  un- 
equal hardness  and  softness  of  the  tissues,  and  a  consequent  in- 
equality of  resistance  to  pressure.  Thus,  if  the  ridge  is  relatively 
28 


434  MECHANICAL    DENTISTRY. 

softer  and  more  compressible  than  the  central  portion  of  the 
arch,  the  plate,  when  force  is  applied  over  the  ridge,  will  "  ride  " 
upon  the  central  portion,  as  upon  a  pivot-point,  and  thus  raise 
or  detach  the  plate  from  the  ridge  on  the  opposite  side.  This  is 
called  "rocking  "  of  the  plate,  the  action  being  illustrated  in  the 
sport  familiarly  known  as  "see-sawing."  Tlic  remedy  for  this 
consists  in  securing  a  space  betiveen  the  central  portion  of  the  roof  of 
the  moiitli  and  the  corresponding  portions  of  the  plate,  so  that  when 
the  substitute  is  applied  to  the  mouth  and  the  air  exliausted,  the 
greatest  pressure  will  be  expended  2ipon  the  ridge,  and,  by  com- 
pression, equalirje  the  resistance.  This  space,  when  the  plastic 
vegetable  bases  are  used,  is  obtained  by  scraping  away  from  the 
impression  at  the  required  points  ;  raising  the  central  portions 
of  the  plaster  model  with  sheet-lead  of  proper  form  and  thick- 
ness;  or  by  trimming  away  from  the  palatal  surface  of  the  fin- 
ished piece.  In  the  case  of  swaged  plates,  the  shrinkage  of  the 
metallic  die  will  ordinarily  afford  the  required  space. 

In  cases  where  there  is  approximate  uniformity  of  hardness  of 
the  ridge  and  central  line  of  the  arch  extending  antero-posteri- 
orly,  associated  with  soft  and  yielding  tissues  filling  the  fosses 
on  either  side  and  extending  some  distance  up  the  lateral  walls 
of  the  arch,  it  is  customary,  in  order  to  equalize  the  pressure  of 
the  plate,  or,  rather,  to  secure  uniformity  of  resistance  to  such 
pressure,  to  scrape  away  from  such  portions  of  the  plaster  model 
as  correspond  with  the  softer  tissues,  thus  securing  in  the  fin- 
ished piece  an  increased  convexity  or  fulness  which,  on  applica- 
tion of  the  substitute,  exerts  a  compressing  force  at  such  points 
superadded  to  that  obtained  either  by  atmospheric  pressure  or 
adhesion.  It  may  be  reasonably  objected  to  this  mode  of  pro- 
cedure that  the  augmented  compressing  force  thus  applied,  being 
continually  antagonized  by  the  inherent  elastic  force  of  the  tissue 
pressed,  must  inevitably  tend  to  weaken  the  attachment  of  the 
substitute,  and  that  such  repelling  force  will  continue  to  act,  in  a 
diminishing  degree,  no  doubt,  until,  from  long-continued  pres- 
sure, such  of  the  tissues  as  are  not  displaced  will  become  ab- 
sorbed or  atrophied.  The  objection  is  emphasized  by  the  further 
fact  that,  in  such  cases,  the  absorption  is  always  preceded  and 
accompanied   by  forcible  displacement  of  superabundant  tissue 


ENTIRE    DENTURES.  435 

into  the  soft  palate,  inducing  more  or  less  irritation  and  ultimate 
chronic  tumefaction  of  the  displaced  tissue  at  the  posterior  mar- 
gin of  the  plate.  The  prevalent  fallacy  that  the  tissues  thus 
subjected  to  pressure  are  condensed  thereby  has  been  considered 
in  the  initial  portion  of  the  chapter  on  impressions. 

No  device  will,  we  believe,  so  effectually  and  satisfactorily 
fulfil  the  requirements  of  the  cases  last  mentioned  as  the  one 
that  provides  for  displacement  of  the  tissues  within  the  limits  of 
the  plate  itself  This  may  be  done  by  securing  a  graduated 
space  including  a  large  part  of  the  palatal  vault.  This  space 
should  not  be  in  the  form  of  a  cavity  with  defined  walls,  but 
should  slope  gradually  toward  the  periphery  in  such  manner 
that  its  boundaries  shall  be  undistinguishable.  By  a  graduated 
cavity  is  meant  that,  wherever  the  soft  tissues  are  in  excess,  there 
should  be  a  corresponding  depth  of  space  to  provide  for  such 
varying  degrees  of  displacement  as  are  essential  in  the  procure- 
ment of  an  equalized  resistance  to  the  pressure  of  the  plate.  By 
this  method,  there  is  not  only  no  injury  or  objectionable  deform- 
ity inflicted,  but  the  attachment  of  the  substitute,  instead  of  being 
impaired,  as  in  the  other  method,  is  maintained  at  first  by  the  full 
and  unobstructed  force  of  atmospheric  pressure,  and  when, 
finally,  the  required  displacement  of  tissue  is  accomplished  by  a 
filling  in  of  the  space,  the  best  practicable  adaptation  is  obtained, 
and  the  future  stability  of  the  substitute  as  perfectly  provided  for 
as  is  possible  with  the  resources  at  our  command. 

Esthetic  Requirements  in  the  Selection  and  Arrangement 
of  the  Teeth  of  Replacement. — In  selecting  teeth  for  an  entire 
upper  and  lower  denture,  the  special  requirements  in  respect  of 
size,  form,  and  color  will  depend  in  a  great  measure  upon  the 
complexion,  age,  sex  ana  general  configuration  of  the  face  of 
the  patient.  Every  separate  denture,  therefore,  that  is  con- 
structed in  strict  conformity  with  a  faithful  interpretation  of  the 
special  requirements  of  each  individual  case,  will  be  character- 
ized by  shades  of  differences  in  color,  form,  size,  and  arrange- 
ment of  the  teeth  of  replacement.  The  indication  in  the  fulfil- 
ment of  such  requirements,  broadly  stated,  is,  that  such  selec- 
tion of  the  teeth,  in  any  given  case,  should  be  made  as  will, 
when  suitably  arranged,  most  perfectly  reproduce  the  lost  pro- 


436  MECHANICAL    DENTISTRY, 

portions    of  the  facial   contour,   and   restore   the  characteristic 
expression  of  the  individual. 

To  accomplish  this  with  fidelity  will  require  a  higher  order  of 
intelligent  discrimination,  and  a  broader  art  culture  than  is  re- 
quired in  cases  where  the  operator  is  aided  by  comparison  of 
the  artificial  with  remaining  natural  teeth,  as  in  partial  dentures. 
In  the  present  case  he  has  no  resources  except  those  that  come 
to  him  through  a  critical  and  conscientious  study  of  the  laws  of 
harmony  as  displayed  in  the  typical  forms  of  dentures  associated 
with  individual  physiognomy  and  temperament.  Says  a  thought- 
ful writer  :*  "  We  find  that  the  necessity  for  art  in  dentistry  exists 
in  proportion  to  the  hopelessness  of  the  case.  The  greater  the 
amount  of  lost  tissue  to  be  replaced,  the  greater  the  knowledge 
of  natural  form  required  to  properly  effect  its  replacement.  Be- 
ginning with  the  restoration  of  portions  of  teeth  through  gold 
fillings,  we  come  to  the  loss  of  the  entire  crown,  and,  finally,  to 
that  last  resort,  the  replacement  of  the  entire  denture.  Knowl- 
edge of  form  and  color,  of  expression,  character,  and  effect,  now 
becomes  imperative  to  the  dentist.  To  relieve  the  condition  of 
his  patient,  the  art  of  the  sculptor  and  colorist  must  be  studied 
with  more  care  than  many  of  us  are  wont  to  give  it,  while  a 
knowledge  of  temperament  and  physiognomy  becomes  an  im- 
portant element  in  our  work." 

"  No  matter  how  anatomically  correct,"  observes  one  of  the 
most  intelligent  contributors  to  the  literature  of  esthetic  den- 
tistry,f  "  or  how  skilfully  adapted  for  speech  and  mastication, 
an  artificial  denture  may  be,  yet,  if  it  bear  not  the  relation  de- 
manded by  age,  temperament,  facial  contour,  etc.,  it  cannot  be 
otherwise  than  that  its  artificiality  will  be  apparent  to  every 
beholder. 

"  This  law  of  correlation,  harmony,  running  through  nature, 
attracts  and  enchants  us  by  an  infinite  diversity  of  manifestations  ; 
the  failure  to  recognize  its  demands  by  art  is  correspondingly 
abhorrent  to  our  sensibilities. 

"  In  the  social  gathering,  a  lady  v/ho   appreciates   the   law  of 

*  Dr.  Eben  M.  Flagg,  Dental  Cosmos,  March,  1881. 
t  Dr.  James  W.  White,  "The  Teeth." 


ENTIRE    DENTURES.  437 

harmony  delights  the  eye  by  the  taste  displayed  in  her  attire, 
another,  though  more  elaborately  and  expensively  adorned,  yet 
failing  to  harmonize  the  details  of  her  costume,  attracts  atten- 
tion only  by  the  impression  of  incongruity.  We  hear  frequently 
from  a  lady  who  is  selecting  a  bonnet,  or  from  a  gentleman  pur- 
chasing a  hat  or  other  article  of  wearing  apparel,  the  question 
to  a  friend,  'Does  this  become  me?'  the  query  indicating  the 
recognition  that,  however  exquisite  the  material  or  excellent  the 
manufacture  of  the  article,  a  certain  law  of  fitness  prevails,  the 
failure  to  comply  with  which  makes  the  wearer  appear  ridiculous. 
We  meet  in  the  street  one  the  color  of  whose  hair  we  expect, 
by  the  law  of  association,  to  be  fair  or  sandy,  and  if  otherwise,  a 
wig  or  a  dye  is  instantly  suggested. 

"  There  is  a  relation  between  the  ph}-sical  form  and  the  voice, 
from  which  we  are  led  to  infer  in  advance  the  character  of  the 
tones  which  from  any  given  individual  may  be  expected.  This 
law  of  association  in  any  case  having  led  us  to  anticipate  a  bass 
voice,  the  anomaly,  should  a  falsetto  greet  us,  is  almost  ludicrous. 

"  There  is  a  similar  relation  between  other  physical  character- 
istics and  the  teeth.  A  broad,  square  face,  or  an  oval ;  a  large, 
coarse-featured  man,  or  a  delicately-organized  woman  ;  a  miss  of 
eighteen  or  a  matron  of  fifty ;  a  brunette  or  a  blonde, — these  and 
other  varieties  present  as  many  differing  types,  with  teeth,  in  size, 
shape,  color,  density,  etc.,  corresponding.  If,  then,  teeth  corre- 
lated in  their  characteristics  to  those  which  nature  assigns  to  one 
class  be  inserted  in  the  mouth  of  one  whose  physical  organiza- 
tion demands  a  different  order,  the  effect  cannot  be  otherwise 
than  displeasing  to  the  eye,  whether  the  observer  be  skilled  in 
perception,  or  intuitively  recognizes  inharmony  without  under- 
standing the  cause." 

Written  or  verbal  instructions  can  do  little  more  than  present 
general  principles  governing  the  selection  of  teeth  for  any  given 
case.  The  completeness  with  which  the  requirements  of  indi- 
vidual cases  are  fulfilled  will  largely  depend  upon  the  operator's 
art  intuitions,  and  his  ability  to  properly  interpret  and  apply  the 
basal  facts  which  an  intelligent  study  of  the  relation  of  physiog- 
nomy and  temperament  to  the  teeth  has  revealed.  The  relations 
of  the  latter  to  the  teeth  have  been  clearly  and  fully  set  forth  in 


43^  MECHANICAL    DENTISTRY. 

tabulated  form  by  Dr.  J,  Foster  Flagg,  which  we  herewith  append. 
The  first  table  relates  to  the  basal  temperaments,  namely,  bilious, 
sanguineous,  nervous,  and  lymphatic,  and  their  general  indica- 
tions ;  the  second,  to  the  teeth  as  indicated  by  temperament. 

A  careful  study  of  these  tables,  the  subject-matter  of  which  is 
by  far  the  most  valuable  contribution  that  has  yet  appeared  in 
connection  with  the  subject  under  consideration,  will  furnish  who- 
ever avails  himself  of  its  practical  suggestions  a  helpful  means 
of  solving  one  of  the  most  difficult  problems  in  prosthetic  prac- 
tice. 

The  following  editorial,  by  Dr.  James  W.  White,  on  "Tem- 
perament in  Relation  to  Teeth,"  suggested,  doubtless,  by  Dr. 
Flagg's  tables,  embodies  not  only  a  discussion  of  the  general 
subject  of  temperaments,  but  some  forcible  and  striking  com- 
mentaries on  the  importance  and  value,  esthetically  considered, 
of  the  indications  furnished  by  temperamental  characteristics  in 
the  intelligent  choice  of  artificial  substitutes  for  special  cases. 
The  importance  of  the  subject  to  which  the  article  relates  will 
justify  its  introduction  here  without  abridgment: — 

"  The  animal  kingdom  is  divided  into  sub-kingdoms,  classes, 
orders,  families,  genera,  species.  A  further  or  sub-division  in- 
cludes in  minor  groups  individuals  whose  salient  characteristics 
are  correspondent  or  similar.  Thus  every  living  creature  has 
certain  physical  peculiarities  by  which  its  position  in  this  classi- 
fication is  determined.  Man,  as  the  head  of  the  animal  kingdom, 
besides  having  his  place  in  this  general  scale,  is  distinguished  by  a 
still  finer  classification  under  the  denomination  of  temperament 
— an  association  of  several  distinguishing  characteristics,  such 
as  size  and  form  of  body,  complexion,  color  of  the  eyes  and 
hair,  and,  to  a  certain  extent,  the  disposition  and  character  of  the 
individual. 

"  Temperament  may  be  defined  as  a  constitutional  organiza- 
tion, depending  primarily  upon  heredity — national  or  ancestral 
— and  consisting  chiefly  in  a  certain  relative  proportion  of  the 
mechanical,  nutritive,  and  nervous  systems,  and  the  relative 
energy  of  the  various  functions  of  the  body — the  reciprocal 
action  of  the  digestive,  respiratory,  circulatory,  and  nervous 
systems.     The  stomach,  liver,  lungs,  heart,   and    brain — diges- 


ENTIRE    DENTURES. 


439 


440 


MECHANICAL    DENTISTRY. 


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ENTIRE    DENTURES.  44 1 

tion,  assimilation,  respiration,  circulation,  and  innervation — 
are  all  factors  in  the  differentiation  of  temperament ;  and 
according  to  the  congenital  predominance  of  one  or  the  other, 
and  the  relative  activity  of  these  functions,  is  the  modification  of 
the  characteristics  of  the  individual  which  assigns  him  to  one  or 
other  of  the  basal  or  mixed  temperaments.  Each  temperament 
is  the  result  as  well  as  the  indication  of  the  preponderance  of 
one  or  another  of  these  systems,  and  of  relative  functional 
activity. 

"  A  perfect  equilibrium  of  the  different  systems  is  rarely,  if 
ever,  presented  in  any  individual.  One  having  a  balance  of  all 
the  temperaments  would  be  temperamentless,  or  of  no  special 
temperament.  It  is  difficult,  in  some  cases,  to  decide  positively 
to  which  variety  a  special  case  belongs,  the  several  tempera- 
ments being  combined  and  blended  in  such  ever-varying  propor- 
tions. Not  infrequently  the  indications  are  even  contradictory, 
and  the  blending  of  several  temperaments  require  a  nice  dis- 
crimination to  define  the  admixture.  The  primary  elements  of 
temperament  are  susceptible  of  such  manifold  combinations  ; 
the  determining  forces  are  so  complex,  and  our  knowledge  of 
their  comparative  values  is  so  limited,  that  no  rule  can  be  given 
which  will  not  fail  in  numerous  instances  to  apply  in  all  respects 
to  individual  cases ;  but  that  there  is  a  general  relation  between 
constitutional  qualities  and  external  signs  does  not  admit  of 
question. 

"  Temperaments  are  readily  divisible  into  four  basal  classes — 
bilious,  sanguineous,  nervous,  and  lymphatic  (see  tables) ;  then 
again  into  sub-classes  of  mixed  temperaments — a  combination 
of  two  or  more  of  the  primary  divisions.  In  these  combina- 
tions one  or  other  of  the  so-called  basal  temperaments  predomi- 
nates, and  a  compound  term  is  used  to  express  the  complexity, 
as,  for  instance,  the  nervo-bilious,  signifying  that  the  bilious 
base — the  foundation  temperament — is  qualified  by  an  admixture 
of  the  nervous  element,  and  so  throughout  the  series.  Twelve 
varieties  of  temperament,  in  addition  to  the  four  basal,  may  thus 
be  designated  by  the  combination  in  pairs  of  the  original  four. 
The  admixture  of  the  peculiarities  of  three  or  of  all  four  of  the 
basal  temperaments  results  in  what  are  denominated  respectively 


442  MECHANICAL    DENTISTRY. 

ternary  and  quaternary  combinations,  which  call  for  nice  dis- 
crimination in  diagnosis ;  but  even  such  complexities  are 
registered  in  the  size,  form,  and  color  of  the  dental  organs. 

"The  value  of  a  practical  application  of  the  study  of  tempera- 
ment in  the  practice  of  dentistry  is  apparent.  That  the  relation 
of  the  teeth  to  temperament  is,  as  a  rule,  ignored  by  those 
engaged  in  prosthetic  dentistry  is  evident  in  the  mouths  of  a 
majority  of  those  who  are  so  unfortunate  as  to  be  under  the 
necessity  of  wearing  substitutes  for  lost  natural  dentures. 

"  A  certain  law  of  harmony  in  nature  between  the  teeth  and 
other  physical  characteristics  necessitates  respect  to  size,  shape, 
color,  and  other  qualities  in  an  artificial  denture,  in  order  that  it 
shall  correspond  with  other  indications  of  temperament ;  and  if 
teeth  correlated  in  their  characteristics  to  those  which  nature 
assigns  to  one  temperament  be  inserted  in  the  mouth  of  one 
whose  physical  organization  demands  a  different  type,  the  effect 
is  abhorrent.  The  artificiality  of  artificial  teeth  is  the  subject  of 
remark  by  those  who  have  little  or  no  conception  of  the  reason 
therefor — simply  an  instinctive  appreciation  of  the  incongruity 
and  unreality.  It  is  indeed  rare  to  see  a  case  in  which  there  is 
occasion  for  a  moment's  hesitation  as  to  the  fact  of  replacement. 
There  is  no  dental  service  that,  from  the  esthetic  standpoint,  is, 
as  a  rule,  so  illy  performed  as  the  prosthetic.  Thousands  of 
dentures  are  constructed  which  serve  the  needs  of  the  wearer 
for  speech  and  mastication,  but  which  are,  nevertheless,  deserv- 
ing of  utter  condemnation  as  art  productions.  More  attention 
has  been  paid  to  the  best  methods  of  restoring  impaired  function 
— securing  comfort  and  usefulness  in  artificial  dentures — than  to 
a  correlation  of  the  substitutes  to  the  physical  characteristics  of 
the  patient. 

"What  is  needed  is  such  an  appreciation  of  the  law  of  corres- 
pondence that  the  dentist  can  cipher  out,  as  by  the  rule  of  three, 
the  character  of  teeth  required  in  the  case  of  an  edentulous 
mouth  with  the  same  precision  as  the  comparative  anatomist 
can  from  a  single  bone  indicate  the  anatomical  structure  of  the 
animal  to  which  it  belonged.  The  probability  is  that  in  many, 
perhaps  in  most,  of  the  cases  of  incongruous  artificial  dentures 
the  fault  is  not  in  carelessness  or  indifference  of  the  dentist,  but 


ENTIRE    DENTURES.  443 

in  failure  to  recognize  the  requirements  of  temperament.  A 
certain  family  resemblance  to  each  other  in  a  set  of  teeth  is  con- 
sidered essential,  but  the  adaptability  of  the  set  as  a  whole  to  a 
given  case  should  be  esteemed  of  even  greater  importance. 
Especially  is  there  a  notable  failure  to  recognize  the  color 
demanded  by  form.  A  set  of  teeth  in  which  not  only  the  rela- 
tive length  and  breadth,  but  every  line  and  curve,  characterize  it 
as  belonging  to  a  certain  temperament,  is,  in  contravention  of 
every  law  of  correspondence,  made  of  a  color  which  was  never 
found  in  nature  associated  with  such  forms.  Thus  we  see  con- 
stantly such  incongruities  as  the  association  of  the  massive  tooth 
of  the  bilious  temperament  wMth  the  pearl-blue  color  belonging 
to  the  nervous  temperament,  and  the  long,  narrow  teeth  of  the 
nervous  temperament  of  bronze-yellow  color  never  seen  in  the 
mouth  of  any  but  those  of  a  bilious  temperament. 

"The  trouble  is  not  with  the  manufacturers  ;  they  supply  the 
demand.  The  fact  is,  the  requirements  of  the  law  of  correspond- 
ence have  not  been  sufficiently  studied  by  the  profession.  The 
first  study  of  the  dentist  who  aspires  to  the  dignity  of  artist, 
when  proposing  to  replace  a  lost  denture,  should  be  how  to 
restore  the  natural  appearance  of  his  patient,  and  this  can  only 
be  effected  through  an  appreciation  and  observance  of  the  tem- 
peramental characteristics  and  the  law  of  correspondence  or 
harmony.  Age  and  sex  may  somewhat  modify  the  requirements 
in  a  given  case,  but  the  basal  fact  on  which  he  should  proceed 
is  temperament.  A  failure  to  recognize  its  demands  will  result 
in  failure — from  an  esthetic  standpoint.  A  knowledge  of  the 
distinguishing  characteristics  of  the  various  temperaments  and 
the  style  of  teeth  which  conform  to  nature's  type  in  the  physical 
organization  marks  the  difference  between  the  dental  mechanic 
and  the  dental  artist." 

The  fulfilment  of  the  highest  art  conceptions  in  the  construc- 
tion of  entire  dentures  is  far  from  being  complete  with  the  mere 
selection  of  teeth  in  conformity  with  temperamental  and  other 
indications.  The  essential  preliminary  step  is  concerned  chiefly 
with  the  form  and  color  of  substitutes,  but  the  highest  attain- 
ments in  the  art  of  replacement  can  never  be  attained  without  an 
intelligent  perception  of  the  esthetic  requirements  which   have 


444 


MECHANICAL    DENTISTRY. 


inseparable  relation  to  the  arraiigeuiciit  of  the  teeth  selected  in 
strict  conformity  with  the  same  law  of  harmony  or  correspond- 
ence that  applies  to  form  and  color.  The  art  of  arrangement  is 
scarcely  less  difficult,  and  certainly  not  less  important,  than  the 
art  of  selection,  and  equal  judgment  and  discrimination  will  be 
required  to  effect  such  an  adjustment  of  the  teeth  as  will  most 
faithfully  serve  to  restore  the  facial  contour  and  characteristic 


Fig.  495. 


^M  '  ^ 


expression  of  the  individual.  This  will,  in  most  cases,  necessitate 
some  deviation  from  the  uniformly  symmetrical  or  ideal  relation 
of  the  teeth  to  each  other  characteristic  of  perfect  regularity  of 
arrangement,  and  which  rarely  exists  except  in  connection  with 
a  perfectly  balanced  development  of  the  jaws  and  teeth,  a  condi- 
tion which  may  be  said  to  be  almost  phenomenal.  Such  an 
arrangement  is  exhibited  in  Fig.  495. 


ENTIRE    DENTURES.  445 

The  kind  or  degree  of  displacement  of  any  particular  tooth  or 
teeth  to  effect  such  irregularity  of  arrangement  as  would  best 
reproduce  the  customary  expression  of  the  indivadual  in  any 
given  case,  cannot,  of  course,  be  here  indicated.  The  operator 
is  necessarily  thrown  upon  his  own  resources  in  determining,  in 
this  respect,  the  necessities  of  individual  cases.  Generally  speak- 
ing, the  changed  relation  of  the  teeth  is,  in  most  part,  confined 
to  the  six  anterior  teeth,  above  and  below,  as  they  are  most 
largely  concerned  in  expression  ;  but  it  may  often  be  extended 
to  the  bicuspids  and  molars,  which  may  be  displaced  within  or 
without  the  arch,  or  given  an  oblique  position,  with  here  and 
there  interdental  spaces,  some  of  which  maybe  wade  enough  to 
suggest  the  loss  of  the  natural  teeth  at  intervals.  The  central 
incisors  may  be  made  to  overlap  each  other,  with  the  laterals  in 
normal  position  ;  or  the  latter  may  be  given  a  position  inside  of 
the  circle,  which  will  give  a  relative  prominence  to  the  centrals 
and  cuspids,  or  they  may  be  partially  rotated  while  retaining  their 
regular  position  in  the  arch,  or  be  made  to  overlap  or  underlap 
the  centrals,  in  which  case  the  latter  maj'' be  made  to  diverge 
somewhat  from  each  other  at  the  points,  leaving  some  space 
between  them. 

There  is  scarcely  any  limit  to  the  capability  of  effecting  mal- 
positions of  the  teeth  or  replacement,  and  this  is  especially  true 
of  those  forms  of  substitution  known  as  continuous-gum  work, 
and  in  the  use  of  celluloid,  either  process,  by  admitting  of  the 
use  of  single,  plain  teeth,  affording  unlimited  opportunities  for 
the  optional  placement  of  the  teeth.  In  the  use  of  sectional 
gum  teeth,  many  of  the  forms  of  dental  irregularity  have  been 
faithfully  reproduced  by  manufacturers,  and,  when  selected  with 
an  intelligent  apprehension  of  their  fitness  for  any  particular 
case,  will  meet  the  ordinary  wants  of  the  practitioner  in  the  use 
of  rubber,  or  a  metallic  plate-base  with  rubber  or  celluloid  attach- 
ment. The  minimum  of  capability  in  effecting  irregularity  of 
arrangement  is  attached  to  soldered  work,  where,  as  is  usually 
the  case,  single  gum  teeth  are  employed. 

It  is  possible  often,  when  teeth  have  been  selected  conforming 
as  nearly  as  practicable  to  the  requirements  of  the  case  in  color, 
to  so  change  the  form  of  the  teeth  by  judicious  grinding  of  the 


446  MECHANICAL    DENTISTRY. 

proximate  surfaces,  cutting  edges  of  the  incisors,  and  the  points 
of  the  cuspids,  and  occluding  surfaces  of  bicuspids  and  molars, 
as  to  greatly  change  the  effect  in  the  mouth,  giving  them  an 
harmonious  expression  impossible  in  the  use  of  manufactured 
teeth  in  their  unchanged  form.  This  is  particularly  observable 
when  they  are  ground  in  imitation  of  the  partial  destruction  of 
the  occluding  surfaces  by  erosion,  a  condition  very  commonly 
associated  with  middle  age.  The  effect  is  still  further  enhanced 
by  coloring  the  portions  of  the  ground  surfaces  in  imitation  of  the 
dark  discoloration  usually  associated  with  exposed  dentine.  This 
may  be  readily  done  in  the  manner  described  in  the  chapter  on 
partial  dentures  mounted  on  metallic  plate-base.  The  same  pro- 
cess of  coloring  may  also  be  applied  to  single  porcelain  teeth 
representing  absorption  or  recession  of  the  gum  at  the  cervix, 
which  is  always  of  a  darker  hue  than  the  crown.  An  additional 
device,  sometimes  employed  to  disguise  the  fact  of  artiiiciality,  is 
that  of  introducing  gold  fillings  into  one  or  more  of  the  front 
teeth.  Cavities  for  this  purpose  are  sometimes  formed  in  porce- 
lain teeth  at  the  time  of  baking.  When  these  are  not  readily 
procured,  the  operator  may  easily  improvise  them.  A  dovetailed 
slot  maybe  ground  in  the  proximate  side  of  a  front  tooth  with  suit- 
ably formed  corundum-disks,  or  a  concave  depression  made  and 
retaining  pits  formed  with  a  hard-tempered  steel  drill.  A  cor- 
respondent of  the  Cosmos  gives  the  following  method  of  using 
the  drill :  "  Use  a  hard-tempered,  spear-pointed  steel  drill  in  the 
engine,  and  while  operating  keep  wet  with  a  solution  of  spirits 
of  camphor  and  spirits  of  turpentine  in  equal  parts.  The  cut- 
ting will  be  facilitated  by  giving  the  hand-piece  a  slight  rotary 
motion.  If  a  contour  filling  is  desired,  grind  off  with  the  corun- 
dum-wheel as  much  as  is  desired  for  '  contour,'  after  which  make 
the  retaining  portion  with  the  drill."  Cavities,  however,  can  be 
formed  with  greater  facility  in  the  use  of  the  diamond  point. 

With  these  general  reflections  concerning  full  dentures,  we 
return  now  to  a  consideration  of  the  mechanical  or  manipulative 
processes  concerned  in  the  construction  of  an  entire  denture 
attached  to  a  swaged  metallic  plate  by  soldering. 


CHAPTER    X. 

ENTIRE    DENTURES   ATTACHED    TO   A   SWAGED    METALLIC 

PLATE-BASE. 

Method  of  Constructing  an  Entire  Upper  Denture 
Mounted  on  a  Swaged  Metallic  Plate-Base. — The  general 
form  and  dimensions  of  the  required  base  to  be  used  as  a  sup- 
port for  a  complete  denture  for  the  upper  jaw  may  first  be  indi- 
cated by  drawn  lines  upon  the  plaster  model,  and  a  sheet-lead 
pattern  obtained  from  this  is  to  serve  as  a  guide  in  securing  the 
form  of  the  plate  to  be  swaged.  The  plate  should  be  made  suf- 
ficiently ample  in  its  dimensions  to  cover  all  the  hard  palate, 
the  alveolar  ridge,  and  all  portions  of  the  external  borders  of 
the  latter  not  directly  encroached  upon  by  the  muscles  and 
reflected  portions  of  the  mucous  membrane  of  the  lips  and 
cheeks. 

Before  swaging,  the  plate  should  be  well  annealed,  and  its 
central  portion  brought  as  nearly  as  possible  to  the  form  of  the 
palatal  face  of  the  die  with  the  mallet,  forcing  the  heel  of  the 
plate  down  in  advance  of  the  portion  covering  the  more  anterior 
concavity  of  the  arch,  preventing  thereby  a  doubling  of  the  pos- 
terior edge  of  the  plate  upon  itself.  This  central  portion  may 
also  be  forced  more  perfectly  into  adaptation  with  a  partial 
counter  (see  progressive  counter-dies,  page  179)  before  swaging 
in  the  ordinary  manner,  and  this  is  advisable  in  all  cases  when 
the  palatal  arch  is  very  deep ;  some  operators,  however,  use  the 
contrivance  invented  by  Dr.  T.  H.  Burras,  of  New  York,  illustrated 
in  Fig.  496.  The  die  and  plate,  as  will  be  seen,  are  placed  near 
the  edge  of  the  bench,  and  the  upper  part  of  the  clamp  adjusted 
over  the  central  portion  of  the  plate  ;  the  two  pieces  are  then 
boundly  firmly  to  the  bench  by  tightening  the  screw.  A  pro- 
tective piece  of  buckskin,  cloth,  or  paper  should  be  placed 
between  the  plate  and  the  clamp  to  prevent  the  former  from 
being  bruised  or  indented.     The  margins  of  the  plate   are  now 

447 


448 


MECHANICAL    DENTISTRY, 


turned  over  upon  the  ridge,  and  if  the  external  borders  of  the  latter 
are  undercut  or  stand  even  vertically,  the  edges  of  the  former 
will  tend  to  double  upon  themselves  at  such  points,  and  hence 
it  will  be  necessary,  before  swaging,  to  split  the  plate  in  front, 
and,  in  some   cases,  on  each   side,  and   wherever  divided,  a  V- 

shaped  piece  may  be  cut  out,  of 
sufficient  width  to  allow  the 
divided  edges  to  overlap  slightly 
when  approximated  in  the  pro- 
cess of  swaging.  The  proxi- 
mate edges  of  the  divided  sec- 
tions should  be  filed  to  a  thin 
edge  before  swaging,  so  that 
when  brought  together  and  sol- 
dered there  will  be  but  little 
additional  thickness  of  the  plate 
at  such  points.  The  cut  por- 
tions should  not  be  soldered 
until  after  a  partial  or  complete 
swaging. 

Having  conformed  the  plate 
as  nearly  as  practicable  to  the 
die  with  the  mallet,  or  with  plate 
forceps  constructed  for  the  purpose  (Fig.  /I97),  it  should  be 
placed  between  the  die  and  counter,  and  the  latter  forced 
together  with  a  heavy  hammer  until  a  tolerably  accurate  coapta- 
tion of  the  plate  is  obtained,  the  latter  being  frequently  annealed 
during  the  process  of  stamping  to  render  it  more  pliable.  At 
first  considerable  yielding  and  consequent  deformity  of  the 
counter-die  will  occur;  hence,  after  partial  swaging,  another 
should  be  substituted  and  the  process  continued  until  the  great- 
est possible  accuracy  of  adaptation  is  secured.  If  the  face  of  the 
die  is  marked  by  prominent  and  sharply  defined  rugae,  or  other 
irregularities,  such  points  will,  to  some  extent,  be  bruised  or 
flattened ;  it  will  therefore  be  expedient  in  such  cases,  and 
better,  perhaps,  in  all,  to  finish  the  swaging  with  a  new  and 
unused  die  and  counter,  in  which  case  two  or  three  moderate, 
steady,  and  well-directed  blows  of  the  hammer  will  be  sufficient. 


ENTIRE  DENTURES  ATTACHED  TO  SWAGED  PLATE-BASE.  449 

If  the  plate  is  brought  into  uniform  contact  with  all  parts  of 
the  face  of  the  die,  this  conformity  is  the  only  reliable  test  of  its 
adaptation  out  of  the  mouth.  In  no  case  will  the  swaged  plate 
fit  the  plaster  model  perfectly,  inasmuch  as  the  unavoidable  con- 
traction of  the  die,  however  slight,  will,  especially  in  deep-arched 
mouths,  cause  the  plate  to  bind  on  the  posterior  and  external 
borders  of  the  ridge,  preventing  it  from  touching  the  floor  of  the 
palate;  while  the  bruising,  though  inconsiderable,  of  the  more 
prominent  points  upon  the  die,  and  a  corresponding  flattening 
of  the  plate  at  such  points,  will  prevent  uniform  contact  of  the 
latter  with  the  unchanged  surface  of  the  plaster  model. 

After  final  swaging,  the  plate  should  be  again  annealed  with  a 
heat  nearly  or  quite  equal  to  that  which  will  be  ultimately  required 

Fig.  497. 


in  soldering ;  after  this,  any  additional  swaging  should  be 
avoided,  unless  the  plate  warps  in  the  heat,  and  which  may  be 
determined  by  applying  it  to  the  die ;  if  any  change  has 
occurred,  it  should  be  reswaged  and  again  annealed  at  a  high 
heat,  and  the  operation  should  be  repeated,  if  necessary,  until 
the  plate  retains  its  integrity  of  form  after  the  last  annealing. 
This  process  of  final  heating  does  not  apply  to  silver  if  in  the 
form  of  a  swaged  plate,  as  this  metal  invariably  suffers  some 
change  of  form  when  subjected  to  an  annealing  heat. 

Modifications  in  the   Form   of    Plates    for  Entire   Upper 

Dentures. — Whenever  a  central  air-chamber  is  employed,  it  may 

be  constructed  in  either  of  the  ways  described  when  treating  of 

partial    atmospheric-pressure   plates.     The    general  form  of  an 

29 


450  MECHANICAL    DENTISTRY. 

entire  upper  denture  with  a  central  chamber,  is  exhibited  in  Fig. 

498.  Other  modifications  in  the  form  of  cavity-plates  for  full 
upper  sets  are  in  limited  use,  as  where  chambers  are  arranged 
one  on  each  side  of  the  sloping  walls  of  the  palate,  or  directly 
over  that  portion  of  the  ridge  previously  occupied  by  the 
anterior  molar  and  the  bicuspids  on  each  side,  as  seen  in  Fig. 

499,  called  "  Lateral  Cavity  Plates."  Whatever  their  general 
utility  may  be,  cases  doubtless  occur  where  they  may  be  advan- 
tageously employed,  separately,  as  shown  in  the  illustration,  or 
in  combination  with  the  central  chamber,  as  when  any  great 
inequality  exists  in  the  hardness  of  the  ridge  and  palate,  such  as 
cannot  be  readily  overcome  by  ordinary  means. 

Fig.  498.  Fig.  499. 


Forming  the  Borders  of  the  Plate. — In  whatever  way  the 
plate  is  formed,  a  notch  or  fissure  of  sufficient  depth  to  receive 
and  permit  an  unobstructed  play  of  the  frenum  of  the  lip  should 
be  formed  in  the  front  part  of  the  plate,  while  the  borders  of  the 
latter  nearly  opposite  the  anterior  molars  on  each  side  should 
be  narrowed  to  prevent  undue  contact  of  its  edges  with  the 
folds  of  the  mucous  membrane  stretching  obliquely  across  from 
the  cheeks  to  the  ridge.  Care  should  also  be  taken  to  trim 
away  from  the  heel  of  the  plate  any  portions  that  might  other- 
wise encroach  upon  the  soft  palate. 

It  is  only  in  the  fewest  number  of  cases  that  a  rim  can  be 
swaged  to  form  a  groove  or  socket  properly  situated  for  the 
reception  of  the  plate  extremities  of  either  single  gum  or  block 
teeth,  as  it  will  usually  be  found  impracticable  to  adjust  the 
gum  extremities  to  the  socket  thus  formed  without  necessitating, 


ENTIRE    DENTURES    ATTACHED    TO    SWAGED    PLATE-BASE.     45  I 

in  some  degree,  a  departure  from  a  just  arrangement  and  antag- 
onism of  the  teeth.  Whenever  it  is  thought  best,  therefore,  to 
rim  the  plate,  it  will  generally  be  necessary  to  adjust  and  solder 
a  separate  strip  to  the  plate  along  its  outer  borders,  and  cover- 
ing somewhat  the  gum  portion  of  the  artificial  teeth  resting  on 
the  plate,  after  the  arrangement  of  the  latter  on  the  base  is 
completed. 

Trying  the  Plate  in  the  Mouth. — After  the  plate  has  been 
worked  as  nearly  as  possible  into  the  required  form,  it  should 
be  applied  to  the  mouth  of  the  patient  to  ascertain  the  correct- 
ness of  its  adaptation  to  the  parts  before  proceeding  further  with 
the  operation.  If  the  adaptation  is  found  imperfect,  the  fault 
lies  either  in  the  impression,  or  in  undue  contraction  of  the  die. 
In  the  former  case,  another  impression  should  be  taken,  and  the 
plate  re-swaged  ;  in  the  latter,  a  less  contractile  metal  or  com- 
pound should  be  employed  in  the  formation  of  the  die.  To 
determine  the  practical  efficiency  of  the  adaptation  and  adher- 
ence of  an  atmospheric-pressure  plate,  various  tests  may  be 
applied.  The  coaptation  of  its  borders  to  the  external  walls  of 
the  ridge  may  be  ascertained  by  inspection,  and  the  patient's 
sense  of  contact  or  non-contact  of  its  central  portion  with  the 
floor  of  the  palate  may,  in  some  degree,  be  relied  on  as  evidence 
of  the  accuracy  of  its  adjustment  to  parts  not  visible.  The 
tenacity  with  which  the  plate  adheres  on  the  application  of 
direct  traction  cannot  always  be  relied  upon,  inasmuch  as  a 
well-fitting  plate  will  sometimes  readily  be  dislodged  in  this 
manner,  while,  on  the  contrary,  one  but  illy  adapted  to  the  parts 
may  require  considerable  force  to  separate  it  from  the  jaw  when 
acted  on  in  the  same  way.  TJie  most  tnistivortliy  test  of  actual  or 
practical  stability  is  firm  pressure  applied  alternately  o:ocr  the  ridge 
071  each  side  and  in  front.  If  the  plate  maintains  its  position  and 
remains  fixed  under  repeated  trials  of  pressure  applied  in  the 
manner  indicated,  the  adaptation  may  be  safely  relied  on  ;  if  it 
slides  upon  the  palate  or  is  easily  disengaged  from  the  mouth, 
the  instability  of  the  plate  may  be  referred  in  many  cases,  not  to 
a  want  of  coaptation,  but  to  a  want  of  uniformity  in  the  condition 
of  the  parts  on  which  the  plate  rests.  These  conditions  have 
already  been  sufficiently  considered. 


452  MECHANICAL    DENTISTRY. 

Method  of  Constructing  an  Entire  Lower  Denture 
Mounted  on  a  Swaged  Metallic  Plate-Base. — Aside  from 
the  differences  in  the  form  of  the  plate,  and  the  manipulations 
incident  thereto,  the  process  of  constructing  a  plate  for  the 
under  jaw  does  not  differ  essentially  from  that  already 
described  in  connection  with  full  upper  dentures. 

If  the  lower  plate  is  constructed  from  a  single  lamina  of  gold 
or  other  metal,  //  should  be  somexvJiat  thicker  than  that  used  in 
7ippcr  cases,  and  shoidd  also  be  of  finer  quality,  diS  the  additional 
thickness  of  the  plate  and  the  peculiar  form  of  the  inferior 
maxilla  render  a  greater  degree  of  pliancy  necessary  in  swaging 
it  to  the  form  of  the  ridge.  The  general  form  of  a  base  for  an 
entire   lower  denture  is  exhibited    in   Fig.   500.     The    internal 

Fig.  500.  Fig.  501, 


border  of  the  plate  should  usually  be  doubled — either  by  turn- 
ing the  edge  over  in  swaging,  or  by  soldering  on  a  narrow  strip 
of  plate  or  half-round  wire. 

A  more  perfect  adaptation  of  the  plate  to  the  ridge  may  be 
obtained  by  the  use  of  a  double  instead  of  a  single  plate,  in 
which  case  a  thin  plate,  not  exceeding  No.  30  of  the  gauge, 
should  be  swaged  to  the  form  of  the  ridge  in  the  first  instance, 
and  then  a  duplicate  plate,  swaging  the  two  together  and  unit- 
ing them  to  each  other  with  solder.  A  plate  of  the  specified 
thickness  may  be  very  readily  and  accurately  conformed  to 
any  irregularities  in  the  ridge,  and  when  the  two  are  united  the 
base  will  be  heavier  and  stronger  than  a  single  lamina  of  the 
ordinary  thickness.     Instead,  however,  of   doubling  the  entire 


ENTIRE    DENTURES    ATTACHED    TO    SWAGED    PLATE-BASE.     453 

plate,  it  will  be  sufficient,  in  most  cases,  to  adapt  the  second 
plate  only  to  the  lingual  surface  of  the  first,  extending  it  up 
from  the  lower  edge  to  a  point  corresponding  as  nearly  as  possi- 
ble with  the  inner  portions  of  the  base  of  the  teeth  when  the 
latter  are  adjusted  to  the  plate  (Fig.  501).  A  moderately  thin 
plate  may,  in  this  manner,  be  used  for  the  primary  base,  while 
the  duplicate  band  will  impart  the  requisite  strength  to  the 
plate,  and,  at  the  same  time,  obviate  the  necessity  of  wiring  its 
lingual  border.  In  adopting  either  of  the  last-named  methods, 
the  plates  after  they  are  united  to  each  other  should  be  again 
swaged  to  correct  any  change  of  form  incident  to  the  use  of 
solder. 

Antagonizing  Model  for  an  Entire  Upper  and  Lower 
Denture. — The  following  method  is  adopted  in  securing  an 
antagonizing  model  for  complete  dentures  : — 

Attach  to  the  ridge  of  each  plate  a  roll  or  strip  of  adhesive 
wax  corresponding  in  width  to  the  length  of  the  teeth  which  will 
be  required  for  each  plate  respectively ;  place  the  plates  with 
the  wax  attached  in  the  mouth,  and  trim  away  from  the  proxi- 
mate edges  of  the  wax  until  the  two  sections  close  upon  each 
other  uniformly  throughout  the  circle  ;  then  cut  away  from  the 
labial  surfaces  of  the  rims  of  wax,  above  and  below,  until  the 
proper  fulness  and  required  contour  of  the  parts  associated  with 
the  lips  and  mouth  are  secured.  The  approximation  of  the  two 
jaws,  when  the  finished  substitutes  are  ultimately  adjusted  to  the 
mouth,  will  depend  altogether  upon  the  aggregate  width  given 
to  the  two  sections  of  wax  at  this  stage  of  the  operation,  and  it 
is,  therefore,  important  that  the  "  bite  "  or  closure  of  the  jaws 
secured  at  this  time  should  be  such  as  will  most  perfectly  fulfil 
the  requirements  of  the  case  in  respect  to  the  utility  and  comfort 
of  the  appliance,  and  the  proper  restoration  of  the  normal  facial 
expression.  If  there  is  any  considerable  change  produced  in 
the  relation  of  the  jaws  habitual  to  them  prior  to  the  loss  of  the 
natural  teeth,  the  characteristic  expression  of  the  individual  will, 
in  some  degree,  be  changed  or  marred ;  an  unaccustomed  and 
restrained  action  will  be  imposed  upon  the  muscles  concerned 
in  the  movements  of  the  lower  jaw,  which  will  render  the  use  of 
the  appliances  at  least  temporarily,  if  not  permanently,  uncomfort- 


454  MECHANICAL    DENTISTRY. 

able  and -fatiguing,  or  even  painful;  while  the  utility  of  the 
fixtures  may  be  impaired  or  wholly  destroyed  by  compelling  a 
particular  application  of  forces  in  mastication  inconsistent  with 
their  stability  in  the  mouth.  No  specific  directions,  of  course, 
can  be  given  that  will  apply  to  all  cases,  but  it  may  be  observed 
that,  ordinarily,  the  two  sections  of  wax  should  be  cut  away  from 
their  approximating  surfaces  until  the  jaws  close  sufficiently  to 
permit  the  edges  of  the  lips  to  rest  easily  and  naturally  upon 
each  other  when  in  a  relaxed  condition,  or  the  upper  rim  may 
extend  somewhat  below  the  margin  of  the  upper  lip,  while  the 
lower  section  of  the  wax  is  cut  away  on  a  level  with  the  lower 
lip,  or  a  little  below  it.  Cases  occur,  however,  where  a  less 
exposure  of  the  upper  portion  of  wax,  even  though  quite  narrow, 
will  be  required;  as  where  the  alveolar  ridge  is  very  deep,  and 
the  lip  covering  it  either  absolutely  or  relatively  short,  or  where 
the  latter  is  retracted,  exposing,  even  when  in  a  state  of  repose, 
a  greater  portion  of  all  of  the  crowns  of  the  teeth,  and  in  extreme 
cases  the  margins  of  the  gum.  Between  the  latter  extreme,  and 
an  inordinate  extension  of  the  upper  lip  below  the  ridge,  all 
intermediate  conditions  occur,  and  the  practitioner,  aiming  to 
produce  an  agreeable,  harmonious,  and  truthful  expression  of 
all  the  parts,  must  rely  wholly  upon  his  judgment  in  reference 
to  the  necessary  approximation  of  the  jaws,  the  restoration  of 
the  natural  fulness  and  contour  of  the  mouth,  and  the  relative 
length  to  be  given  to  the  upper  and  lower  teeth. 

Patients  when  requested  to  close  the  mouth  naUirally  are  very 
liable  to  project  the  under  jaw  ;  hence  it  is  well  to  have  them  open 
and  close  the  jaws  frequently,  observing  at  the  same  time  if  the 
separate  portions  of  wax  meet  in, precisely  the  same  manner  at 
each  occlusion.  If  the  bite  varies  at  every  approximation  of 
the  jaws,  the  patient  should  be  directed  to  relax  and  abandon 
for  the  moment  all  control  over  the  muscles  of  the  lower  jaw  ; 
the  operator  should  then  grasp  the  chin  and  press  the  jaw  first 
directly  backward  and  then  upward  until  the  opposing  surfaces 
of  the  wax  meet,  in  which  position  it  should  be  steadily  held  by 
the  patient  until  the  two  portions  of  wax  are  attached  to  each 
other  in  that  particular  relation.  The  latter  may  be  done  by 
drawing  lines  vertically  across  the  rims  of  wax  at  various  points, 


ENTIRE    DENTURES    ATTACHED    TO    SWAGED    PLATE-BASE.     455 


which  will  serve  to  indicate  their  relation  to  each  other  when 
out  of  the  mouth  ;  or  a  heated  knife-blade  may  be  passed  be- 
tween the  two  sections,  the  melted  wax  temporarily  uniting  them. 
A  very  convenient  and  secure  method  is  to  attach  them  together 
by  means  of  two  strips  of  metal  bent  in  the  fonp  of  a  staple  ; 
these  may  be  warmed  in  a  spirit-flame,  and  pressed  into  the  wax, 
one  on  each  side — one  end  penetrating  the  upper  rim  of  wax, 
the  other  the  lower.  Before  removing  the  plates,  the  mesial 
line  of  the  mouth  should  be  indicated  upon  the  wax  by  drawing 
a  line  vertically  across  the  latter  in  front,  to  serve  as  a  guide  in 
the  arrangement  of  the  central  incisors. 

The  plates,  attaclied  to  each  otJicr  (as  shown  in  Fig.  502),  may 
be  removed  from  the  mouth, 

plaster  mixed  and  poured  into  l^i^-  502. 

them  to  form  temporary 
models  for  attachment  in  the 
articulator.  When  the  plaster 
is  sufficiently  condensed,  the 
line  across  the  wax  in  front 
should  be  extended  in  a 
direct  line  across  tiie  bor- 
ders of  the  plaster  model 
above  and  below,  as,  in  ar- 
ranging   the    teeth,   the    wax 

will  be  removed,  and  without  this  precaution  the  mesial  point  of 
the  mouth  may  be  lost. 

Antagonizing  Model  for  an  Entire  Upper  Denture  with 
the  Natural  Teeth  of  the  Lower  Jaw  Remaining. — In  form- 
ing an  antagonizing  model  to  be  used  as  a  guide  in  arranging 
and  articulating  a  full  upper  denture  where  all  or  a  part  of  the 
natural  organs  of  the  inferior  jaw  are  remaining,  a  rim  of  wax 
should  first  be  adjusted  to  the  borders  of  the  plate,  one  or  two 
lines  wider  than  the  required  length  of  the  artificial  teeth. 
When  placed  in  the  mouth,  the  exterior  surface  of  the  wax  draft 
■should  be  cut  away  or  added  to  until  the  proper  fulness  of  the 
parts  is  restored.  The  patient  should  then  close  the  lower 
teeth  against  the  wax,  embedding  them  just  siifficiently  to  indicate 
the  cutting  edges  and  grinding  surfaces.     The  median  line  of  the 


456 


MECHANICAL    DENTISTRY. 


mouth  is  then  indicated  upon  the  wax  and  the  plate  removed, 
when  the  two  casts  (the  lower  having  been  previously  secured 
from  a  wax  or  modeling  compound  impression),  should  be 
secured  in  the  articulator  shown  in  Fig.  491. 

Articulators. — Various  articulators  have  been  devised.  Fig. 
503  illustrates  one  of  the  simpler  forms,  while  a  very  ingenious 
and  novel  device  has  been  brought  to  the  notice  of  the  profes- 
sion by  Dr.  W.  G.  A.  Bonwill,  of  Philadelphia,  to  which  we  give 
considerable  space.  The  inventor  has  characterized  it  as  the 
''Anatomical  Artiailator','  and  describes  it  as  follows  : — 

Fig.  503. 


"  It  is  modeled  on  the  same  geometrical  system  as  the  human 
jaw. 

"  I  found  by  measurement  that  the  average  width  of  the  lower 
jaw  from  center  to  center  of  each  condyle  was  four  (4)  inches, 
and  from  the  same  center  of  each  condyloid  process  to  the 
median  line  of  the  lower  jaw,  where  the  cutting  edges  of  the 
lower  incisors  meet,  was  also  four  (4)  inches,  making  of  the  human 
jaw  an  equilateral  triangle.  This  holds  good  in  all  jaws,  and  the 
difference  of  a  quarter  of  an  inch  in  this  radius  of  a  circle  of  four 
inches  would  make  but  little  practical  difference  as  to  the  results. 


ENTIRE    DENTURES    ATTACHED    TO    SWAGED    PLATE-BASE.     457 

"  This  beautiful  law  enables  us  to  have  the  fullest  benefit  of 
mastication  at  the  least  expense  of  power  and  motion  in  the  arc 
of  the  circle  of  four  inches  as  a  radius. 

"  This  being  an  absolute  law,  I  have  so  made  this  articulator, 
and  the  cast  of  every  case  is  set  therein  with  the  median  line  at 
the  lower  centrals  just  four  inches,  by  the  dividers,  from  each 
condyloid  process.  If  an  unusually  large  jaw,  then  the  cast  is 
put  a  very  little  distance  further  out. 

"  For  all  full  sets,  the  articulation  is  so  perfect,  as  made  in 
this,  in  the  laboratory,  as  to  need  but  a  trifling  touch  in  fitting 
in  the  mouth. 

"  I  found  that  there  is  a  further  positive  law  in  the  mechanism 
of  the  human  jaw  that  should  be  regarded  in  every  substitute  made 
therefor,  and  that  is,  just  in  proportion  to  the  depth  of  overbite  of 
the  centrals,  there  is  a  curvature  from  the  mesial  surface  of  the 
first  molars  back,  through  the  other  molars,  up  the  ramus.  That 
this  curvature  upward  and  backward  at  the  ramus  is  due  solely 
to  the  depth  of  closure  of  the  upper  over  the  lower  jaw.  That 
where  there  is  occlusion  or  closing  of  the  cutting  surfaces  of  the 
incisors  directly  upon  each  other,  then  a  straight  line,  directly 
backward,  is  the  consequence.  If  curved  at  the  ramus,  in  such 
a  case  no  lateral  or  forward  movement  of  the  lower  jaw  could 
occur — only  the  up  and  down. 

"  When  there  is  an  eighth  of  an  inch  depth  of  bite,  then,  as 
you  go  back  to  the  center  of  motion — the  condyloid  processes — 
the  cusps  in  the  bicuspids  and  molars  grow  less  deep,  and  the 
curvature  at  the  ramus  is  an  eighth  of  an  inch  out  of  line. 

"  When  there  is  an  overbite  of  an  eighth  of  an  inch,  then,  in 
opening  the  lower  jaw  and  carrying  it  forward  to  use  the  incisors 
for  cutting,  the  back  teeth  of  the  lower  jaw  are  brought  forward  ; 
and  as  the  second  molar  is  higher  out  of  line  than  the  first 
molar,  it  comes  in  contact  with  the  distal  surface  of  the  first 
superior  molar,  which  begins  just  here  to  curve  upward,  and  is 
the  highest  out  of  line  in  the  superior  jaw,  and  they  meet  at  the 
same  time  that  the  incisors  do.  And  the  same  law  holds  good 
when  the  lower  jaw  is  turned  to  the  right  or  left;  the  molars  are 
brought  in  contact  to  equalize  the  force  which  would  be  brought 
upon  the   incisors  only.     Besides,  the  recognizing  of  this  law 


458  MECHANICAL    DENTISTRY. 

enables  the  cusps  or  palatal  and  lingual  sides  of  the  molai-s  of 
both  jaws  to  be  utilized  in  every  position  the  lower  jaw  may- 
take  in  mastication.  Upon  this  plan  I  make  all  my  artificial 
dentures,  most  of  their  articulating  surfaces  being  utilized  at 
every  position  of  the  lower  jaw.  Any  human  jaw  will  show 
this  system,  which,  by  this  system  can  be  made  just  as  complete, 
and  more  so,  in  many  cases,  than  the  normal,  or  such  as  is  found 
in  advanced  civilization. 

"  When  a  set  of  teeth  is  commenced  in  this  articulator  with  the 
upper  overbiting  the  lower  an  eighth  of  an  inch,  as  you  set  each 
tooth  backward  toward  the  condyloid  processes  they  will  assume 
the  exact  angle  and  depth  of  cusps,  as  well  as  the  curvature  at  the 
ramus,  as  found  in  nature.     If  both  jaws  are  in  direct  opposition 

Fir,.  504. 


at  the  incisors,  then  all  of  the  teeth  must  of  necessity  be  on  a 
perfect  plane,  or  but  one  would  touch  when  in  lateral  position. 

"  With  this  one  base,  which  Fig.  504  shows,  there  is  a  separate 
bow  to  each  part  of  base,  one  for  upper  and  one  for  lower  jaw, 
which  can  be  removed  as  soon  as  the  plaster  in  one  case  is  allowed 
to  harden  on  the  rim.  This  can  be  marked  and  laid  away  for  a 
year  if  necessary,  and  then  articulated.  A  pair  of  bows  can  be 
used  for  as  many  separate  cases,  while  only  one  base  is  required, 
which  should  be  made  absolutely  and  geometrically  exact — 
approximately  so. 

"  There  is  no  need  for  set  screws  to  hold  the  bows,  as  they  go 
up  just  so  far  and  remain  so.  Nor  is  there  any  set  screw  and  prop 
to  hold  the  jaws  or  casts  apart.  This  is  regulated  on  the  bite  in 
wax,  which,  before  it  is  taken   off  the  base  plate,  has  the  exact 


ENTIRE    DENTURES    ATTACHED    TO    SWAGED    PLATE-BASE.     459 

height  marked  by  a  pair  of  dividers  on  the  plaster  at  the  median 
hne,  measuring  from  the  cutting  edge  of  wax,  and  then,  when 
the  first  central  or  block  is  set,  there  is  no  longer  any  call  for  a 
prop  to  keep  open  the  jaws  of  the  articulator.  When  this 
height  is  taken  with  the  dividers,  it  is  marked  on  the  top  of  each 
cast  for  future  reference.  It  would  interfere  with  the  lateral 
movement  if  a  rigid  prop  were  there.  The  dividers  make  each 
case  exact  without  a  scale  for  measurement. 

"  Articulate  the  upper  set  first,  and  retain  on  the  lower  base 
the  wax  for  length  and  fulness.  When  the  upper  are  all  on,  then 
the  lower  incisors  are  gauged  as  to  the  height  or  length  by  the 
dividers  while  the  wax  is  still  on  the  base  plate  and  taken  from 
the  height  marked  on  the  lower  cast  for  reference. 

"  Make  the  lateral  movement  as  soon  as  the  first  tooth  or  block 
is  in  position  where  the  case  is  an  upper  one  with  a  good  lower 
jaw  of  natural  teeth. 

"  When  a  full  set,  the  upper  are  first  ground  on  and  shaped  so 
as  to  meet  the  intended  overbite,  and  when  the  lower  set  are 
ground  on,  the  upper  can  be  changed  to  suit  the  lower,  so  as  to 
allow  the  whole  of  every  cusp  to  touch  at  nearly  every  lateral 
movement  of  jaw. 

"  When  the  plaster  case  is  to  be  set  in  the  articulator,  it  must 
be  done  with  the  dividers  set  just  four  (4)  inches,  with  one  point 
at  the  median  line  as  formed  by  the  lov/er  incisors,  and  the  other 
carried  over  to  each  condyloid  process  as  marked  on  the  articu- 
lator. This  makes  the  center  of  jaw  equidistant  from  the  con- 
dyles. The  study  of  this  principle  will  make  one  fully  realize  the 
beautiful  workings  of  Divinity,  which  is  only  governed  by  posi- 
tive law  in  every  department  of  the  universe.  With  this  plan 
understood,  one  will  never  again  attempt  to  articulate  a  set  of 
teeth  on  the  unwritten  law,  as  now  universally  made  and  recog- 
nized by  every  dentist  in  the  land. 

"  Until  this  system  is  taught  in  the  schools  and  by  private 
practitioners,  no  truly  artistic  and  fully  natural  set  of  teeth  can 
ever  be  made,  for  we  have  been  without  law  in  this  department. 
To  describe  it  is  not  enough.  It  must  be  seen  and  demonstrated, 
one  tooth  at  a  time,  until  the  whole  set  is  made.  Only  in  this 
way  can  it  be  understood. 


460  MECHANICAL    DENTISTRY. 

"The  Figs.  504  and  505  show  clearly  the  simple  construction. 
It  is  made  of  brass  wire  (one-eighth  inch  in  diameter),  and  brass 
tubing  to  allow  the  size  of  wire  to  fit  closely,  and  move  freely 
therein  when  drawn  out  or  pushed  up.  The  spiral  spring  on 
either  condyle  allows  of  easy  lateral  motion  to  the  lower  part, 
and  from  exactly  the  same  standpoint  as  in  nature ;  that  is,  one 
of  the  lower  condyles  moves  forward  in  the  glenoid  cavity  while 
the  other  remains  still.  Every  part  of  it  is  rigid  except  the 
movement  at  the  condyles,  and  the  joints  or  bows  are  only  tem- 
porarily so.  There  is  also  an  up-and-down  motion  made  at  the 
condyles  by  raising  the  bow  up  or  down. 

"  No  case,  when  once  fixed  in  it,  can  become  disarranged.  If 
the  bite  in  the  wax  is  not  correct,  no  articulator  can  make  it  so. 

Fir,.  505. 


You  must  go  back  again  to  the  mouth  and  retake  it,  which  is 
easily  done  at  first  by  asking  the  patient  to  swallow,  when  the 
jaws  will  automatically  close  and  assume  their  normal  position. 
If  now  correct,  there  is  never  any  necessity  for  a  screw  to  change 
it  when  once  in  this  articulator. 

"  There  can  be  no  excuse  for  failure  or  unartistic  work  when 
this  instrument  is  once  understood  and  the  law  controlling  the 
human  jaw.  As  we  may  forever  have  to  resort  to  artificial  den- 
tures, we  should  demand  of  the  colleges  that  such  an  instrument 
be  used,  and  it  alone,  as  furnishing  the  only  hope  now  offered 
of  an  approach  to  high-toned,  artistic  mechanical  dentistry. 
Until  we  can  be  taught  to  appreciate  that  law  is  the  governor  of 
the  universe,  and  applicable  in  every  branch  of  dentistry,  we  are 


ENTIRE    DENTURES    ATTACHED    TO    SWAGED    PLATE-BASE.     46 1 

false  men,  and  will  set  '  false  teeth,'  and  never  realize  our  high 
destiny." 

Grinding  and  Adjusting  Single  Gum  Teeth. — In  arranging 
or  adjusting  single  gum  teeth  to  the  plate  in  those  cases  where 
the  changes  in  the  form  of  the  alveolar  ridge,  consequent 
on  absorption,  are  completed,  the  portions  applied  to  the  base 
should  be  ground  away  sufficiently  to  restore  the  required 
fulness  of  the  parts  and  to  give  proper  length  and  inclination 
to  the  teeth.  The  coaptation  of  the  ground  surfaces  to  the 
base  should  be  accurate  enough  to  exclude  perfectly  par- 
ticles of  food,  and  to  furnish  such  a  basis  to  each  tooth  as  will 
provide  most  effectually  against  fracture  when  acted  upon  by  the 
forces  applied  to  them  in  the  mouth.  The  gum  extremities  of 
the  teeth  should  also  be  accurately  united  to  each  other  lateralh- 
by  grinding  carefully  from  their  proximate  edges  until  the  joints 
or  seams  will  be  rendered  incapable  of  ready  detection  in  the 
mouth,  care  being  taken  that  this  coaptation  of  the  adjoining 
surfaces  is  uniform,  for  if  confined  to  the  outer  edge  alone,  por- 
tions of  the  gum  enamel  may  be  broken  away  in  the  process 
of  soldering. 

Arranging  for  Temporary  Plates. — In  the  construction  of 
substitutes  designed  to  fulfil  only  a  temporary  purpose,  and 
where  the  alveolar  processes  remain  in  a  great  measure  unab- 
sorbed,  and  plain  teeth  (those  representing  but  the  crowns  of  the 
natural  organs)  are  used,  but  little  skill  will  ordinarily  be  required 
in  adjusting  and  fitting  them  to  the  base.  If  the  ridge  in  front 
is  prominent  and  but  inadequately  concealed  by  the  lip,  as 
where  the  teeth  have  been  but  recently  extracted,  all  those  por- 
tions of  the  border  of  the  plate  in  front,  anterior  to  the  first  or 
second  bicuspid  on  each  side,  may  be  cut  away  on  a  line  a  little 
within  the  required  circle  of  the  anterior  teeth  and  scalloped,  per- 
mitting the  anterior  cervical  portions  of  the  artificial  incisors  and 
canines,  and,  in  some  cases,  the  anterior  bicuspids,  to  overlap  the 
edge  of  the  plate  and  rest  directly  and  firmly  upon  the  gum  in 
front.  This  abridgment  of  the  plate  will  not  ordinarily,  materialh" 
affect  the  adhesion  or  stability  of  the  substitute. 

There  are  cases  of  a  mixed  character  that  render  it  more  diffi- 
cult to  effect  a  harmonious  and  symmetrical  arrangement  of  the 


462  MECHANICAL    DENTISTRY. 

teeth,  as  where  a  Hinited  number  of  the  natural  teeth  at  interva4s 
have  been  long  absent,  and  the  excavations  in  the  ridge  conse- 
quent on  absorption  alternate  with  other  points  upon  the  ridge 
in  a  comparatively  unchanged  condition.  To  give  uniformity 
to  the  denture  by  restoring  perfectly  the  required  circle  of  the 
arch  in  such  cases  will  necessitate  the  employment  of  plain  and 
single  gum  teeth  conjointly.  Whenever  necessary,  those  por- 
tions of  the  base  occupied  by  the  plate  teeth  may  be  cut  away 
in  such  a  manner  as  to  permit  the  latter  to  be  adjusted  directly 
to  the  unabsorbed  gum  as  before  described. 

Arranging  the  Teeth  for  a  Full  Upper  and  Lower  Denture. 
— In  the  process  of  grinding  the  teeth  to  the  base,  above  and 
below,  the  operator  should  commence  by  first  arranging  the 
superior  central  incisors,  and  then  the  lower,  and  so,  passing  back 
from  tooth  to  tooth,  grind  and  adjust  an  upper  and  lower  tooth 
alternately,  keeping  the  upper  ones  in  advance  of  those  of  the 

lower  jaw.     The  central  incisors 
^'^'-  5°6-  above  should  be  placed  parallel 

with  each  other,  but  the  cutting 
edges  of  the  laterals  and  the 
points  of  the  canines  should  in- 
cline slightly  toward  the  median 
line  of  the  mouth.  In  arranging 
the  teeth  of  the  upper  jaw,  the 
anterior  six  may  be  made  to  de- 
scribe, with  more  or  less  exact- 
ness, the  segment  of  a  circle,  but 
a  somewhat  abrupt  angle  may 
be  given  to  the  arch  on  each  side  by  placing  the  first  bicuspid 
within  the  circle  in  such  a  way  that,  when  standing  directly  in 
front  of  the  patient  and  looking  into  the  mouth,  only  a  narrow 
line  of  the  exterior  face  of  the  crowns  of  these  teeth  will  be 
seen,  while  the  remaining  teeth  posterior  to  them  should  be 
arranged  nearly  on  a  straight  line,  diverging  as  they  pass  back- 
ward. When  arranged  in  the  manner  described,  the  peripheral 
outline  of  the  arch  will  exhibit  somewhat  the  form  presented  in 
the  diagram  (Fig.  506). 

In  regard  to  the  practical  efficiency  of  an  upper  denture  re- 


ENTIRE  DENTURES  ATTACHED  TO  SWAGED  PLATE-BASE.  463 

tained  in  the  mouth  by  atmospheric  pressure  or  adhesion,  it  is 
important  that  the  teeth  engaged  in  the  comminution  of  food,  as 
the  bicuspids  and  molars,  should  occupy  a  position  directly  over 
the  central  line  of  the  ridge,  and  should  either  be  arranged  ver- 
tically or  with  a  slight  inclination  toward  the  center  of  the  mouth. 
The  liability  to  displacement  of  the  substitute  in  mastication  will 
thus  be  greatly  diminished,  whereas,  if  placed  outside  of  the  line 
indicated,  and  especially  with  a  diverging  inclination,  the  sta- 
bility of  the  appliance  will  be  endangered  and  the  functions  of 
mastication  impeded,  notwithstanding  other  conditions  necessary 
to  complete  success  have  been  fully  secured.  In  arranging  the 
upper  and  posterior  teeth  as  described,  it  will  sometimes  be 
necessary  to  give  to  the  opposing  under  teeth  a  decided  inward 
inclination  in  order  to  effect  a  satisfactory  antagonism  of  the 
teeth;  and  cases  occur  where  a  practical  articulation  cannot  be 
secured  without  departing  in  some  degree  from  the  arrangement 
of  the  upper  teeth  spoken  of, — as  where  a  great  disparity  exists 
between  the  posterior  transverse  diameters  of  the  two  jaws,  a 
medium-sized,  or  even  small,  arch  above  being  associated  with 
an  expanded  ridge  below. 

In  articulating  the  upper  and  lower  teeth,  the  normal  occlu- 
sion of  the  natural  organs  should  be  imitated  as  nearly  as  the 
other  essential  requirements  of  the  case  will  admit.  Hence 
the  upper  front  teeth,  describing  the  segment  of  a  larger  circle 
than  the  corresponding  teeth  of .  the  lower  jaw,  will  project 
beyond  and  overlap  slightly  the  cutting  edges  of  the  latter  ; 
and  having  a  greater  width  of  crown,  they  will  extend  laterally 
beyond  the  opposing  teeth,  covering  one-third  of  the  crowns  of 
those  next  adjoining,  so  that  when  the  canines  of  the  upper  jaw 
are  reached  they  will  close  between  the  lower  canines  and  first 
bicuspids  ;  and,  passing  back,  the  anterior  superior  bicuspids 
between  the  first  and  second  bicuspids  below ;  the  posterior 
bicuspids  above,  between  the  second  inferior  bicuspids  and 
anterior  molars ;  the  first  superior  molars  between  the  first  and 
second  molars  below ;  while  the  anterior  half  of  the  posterior 
molars  above  will  close  upon  the  posterior  half  of  the  inferior 
second  molars,  the  remaining  posterior  half  of  the  second 
molars  above  extending  posteriorly  beyond  those  of  the  lower 


464  MECHANICAL    DENTISTRY. 

jaw.  The  outer  cusps  of  the  superior  bicuspids  and  molars  will 
overlap  those  of  the  inferior  teeth  ;  while  the  inner  cusps  of  the 
teeth  of  the  superior  jaw  will  pass  into  the  depressions  in  the 
lower  teeth  formed  by  the  internal  and  external  cusps,  and  the 
external  cusps  of  the  inferior  teeth  will,  in  like  manner,  be 
received  into  the  corresponding  excavations  of  the  upper  teeth. 
An  abnormal  relation  of  the'  jaws,  as  where  undue  projection, 
absolutely  or  relatively,  of  either  maxilla  exists,  or  where  the 
lower  jaw  closes  on  one  side  or  other  of  the  upper,  will 
frequently  compel  a  departure  from  the  ordinary  arrangement  of 
the  artificial  organs,  the  extent  of  which  must  be  determined  by 
the  necessities  of  each  individual  case. 

In  selecting  teeth  for  a  full  upper  denture  in  those  cases 
where  natural  teeth  are  remaining  below,  or  vice  versa,  the 
color,  size,  and  form  of  the  latter  will  serve  as  a  guide  in  the 
choice  of  teeth  appropriate  for  the  opposite  jaw.  In  fitting  and 
arranging  the  teeth  upon  the  base,  and  in  antagonizing  them 
with  the  opposing  natural  teeth,  the  same  general  principles 
apply  as  those  already  adverted  to  in  connection  with  full  upper 
and  lower  dentures. 

Having  adjusted  the  teeth  to  the  base,  they  should  be  placed 
in  the  mouth  before  uniting  them  permanently  to  the  plate,  to 
detect  and  remedy  any  error  of  arrangement  either  in  respect  to 
prominence,  position,  inclination,  length,  or  antagonism. 

Forming  a  Rim  to  the  Plate. — If  the  case  is  one  where 
single  gum  or  block  teeth  are  employed,  and  it  is  intended  to 
form  a  socket  or  groove  upon  the  borders  of  the  plate  for  the 
reception  of  the  plate  extremities  of  the  teeth,  the  rim  forming 
the  groove  should  be  fitted  and  soldered  to  the  base  before 
investing  the  piece  in  plaster.  If  the  alveolar  ridge  above  is 
shalloiv,  and  but  imperfectly  concealed  by  the  lip,  a  rim  to  the  plate 
zvill  be  inadmissible,  as,  when  the  mouth  is  opened  and  the  lip 
retracted,  as  in  laughing,  the  metallic  band  will  be  exposed  to 
view.  A  rim  may  be  fitted  and  attached  to  the  base  in  either  of 
the  following  ways  : — 

I.  A  strip  of  plate  from  one  to  two  lines  in  width  is  adjusted 
to  the  plate,  with  one  edge  resting  on  the  uncovered  border  of 
the  plate  close  to  the  gum  extremities  of  the  teeth,  and  the  other 


ENTIRE    DENTURES    ATTACHED    TO    SWAGED    PLATE-BASE.     465 

overlapping  and  embracing  the  latter.  The  rim  may  be  more 
conveniently  adjusted  by  employing  two  pieces,  extending  from 
each  heel  of  the  plate  and  uniting  in  front. 

2.  A  half-round  wire  with  the  edge  beveled  where  it  joins  the 
ends  of  the  teeth,  forming  a  narrow  groove,  may,  in  like  man- 
ner, be  fitted  to  the  plate,  furnishing  a  shallow  bed  for  the  gum 
extremities  of  the  teeth.  A  narrow  strip  of  plate,  about  the 
thickness  of  heavy  clasp  material,  may  be  substituted  for  the 
half-round  wire.  In  either  case,  the  better  plan  is  first  to  trace 
the  outlines  of  the  gum  portions  of  the  teeth  upon  the  plate 
with  a  sharp  instrument ;  remove  the  wax  and  teeth  from  the 
plate;  draw  another  line  a  little  within  the  first  all  round,  and 
solder  the  rim  to  the  line  last  drawn ;  remove  the  teeth  from 
the  wax,  and  readjust  the  latter  in  its  proper  place  upon  the 
plate ;  then  fit  each  tooth  separately  to  the  rim  by  grinding 
away  sufficiently  from  the  end  of  the  tooth  to  effect  an  accurate 
adjustment  of  it  to  the  socket.  The  ends  of  the  teeth  may  be 
ground  away  to  the  rim  until  the  platinum  pins  freely  re-enter 
the  rivet-holes  in  the  wax,  thus  restoring  them  to  their  proper 
position  in  relation  to  the  base. 

3.  Another  method  of  forming  a  rim,  and  probably  the  best, 
consists  in  swaging  a  strip  of  plate  accurately  to  the  form  of  the 
parts  to  which  it  is  applied.  An  impression  in  wax  or  plaster  is 
first  taken  of  the  gum  surfaces  of  the  teeth  and  exposed  border 
of  the  plate  ;  but  as  it  will  be  impossible  to  detach  either  wax  or 
plaster  in  perfect  condition  when  encircling  the  entire  arch,  or 
to  swage  perfectly  with  a  die  so  unfavorably  formed  for  stamp- 
ing, separate  impressions  of  the  two  lateral  halves  of  the  piece 
should  be  taken  from  these  plaster  models,  and  from  the 
latter,  dies  and  counters ; — with  these,  two  strips  of  plate  of 
sufficient  width  are  swaged,  each  extending  from  the  heel  of 
the  plate  to  a  little  beyond  the  median  line  in  front,  overlapping 
slightly  at  the  latter  point.  The  portions  of  the  swaged  strips 
embracing  the  plate  ends  of  the  teeth  are  then  trimmed  to  the 
proper  width,  and  scalloped,  if  desired,  in  correspondence  with 
the  festoons  of  the  artificial  gums.  In  whatever  way  the  rim  is 
formed,  when  it  has  been  fitted  to  the  plate  and  teeth  it  may  be 
held  temporarily  in  place  with  clamps  adjusted  at   two  or  three 

30 


466  MECHANICAL    DENTISTRY. 

points  around  the  plate  and  then  transferred  to  a  piece  of  char- 
coal, and  secured  by  first  tacking  it  at  two  or  three  points  with 
solder.  The  groove  may  then  be  filled  with  whiting,  mixed 
with  water  or  alcohol,  to  prevent  the  solder  from  flowing  in  and 
filling  it  up ;  after  which  small  pieces  of  solder  are  placed  along 
the  line  of  union  next  the  edge  of  the  plate,  and  the  rim  perma- 
nently united  throughout  with  the  blowpipe ;  after  which  the 
wax  and  teeth  are  reapplied  to  the  plate. 

Constructing  and  Attaching  Spiral  Springs. — The  success 
which  has  been  attained  in  the  use  of  atmospheric  pressure  and 
adhesive  plates  has  almost  entirely  superseded  the  necessity  of 
employing  spiral  springs  as  means  of  support ;  nor  should  the 
latter  be  resorted  to  except  under  circumstances  that  preclude 
the  use  of  the  former,  as   in  case  of  cleft  palate,  for  instance. 

Fig.  507. 


^ 


When  applied,  they  should  be  attached  to  the  base  on  each  side 
between  the  posterior  bicuspid  and  first  molar  below,  and  opposite 
the  posterior  bicuspid  above.  To  the  border  of  the  plate  near  the 
base  of  the  teeth  a  narrow  strip  of  plate  is  soldered,  extending 
up  and  lying  closely  against  the  side  of  the  latter,  to  the  end  of 
which,  near  the  grinding  surfaces  of  the  teeth,  is  adjusted  a  small, 
circular  cap  of  gold  connected  with  the  standard  by  a  small 
wire  on  which  the  looped  extremity  of  the  spring  plays.  To 
each  end  of  the  spring  is  attached  a  gold  wire,  doubled  upon 
itself  in  such  a  way  as  to  form  a  loop,  the  closed  ends  being 
soldered  together  and  filed  to  enter  the  hollow  in  the  wire,  A, 
Fig-  507.  B,  Fig.  507,  copied  from  Professor  Harris's  work  on 
dental  surgery,  represents  another  method  of  attaching  springs, 
but  the  former  is  more  readily  constructed  and  will  answer  every 


ENTIRE  DENTURES  ATTACHED  TO  SWAGED  PLATE-BASE.  467 

practical  purpose.  Figs.  508  and  509  exhibit  the  application  of 
springs  to  an  upper  and  lower  denture.  In  this  instance  plain 
teeth  are  shown,  but  they  may  be  readily  attached  to  either 
plain  or  gum  teeth. 

Investing. — The  plate,  with  the  wax  and  teeth  in  place,  is 
next  encased  in  a  mixture  of  plaster  preparatory  to  backing  the 
teeth  and  uniting  them  with  solder  to  the  base.  For  this  purpose, 
plaster  and  sand  may  be  employed,  using  as  little  of  the  former  as 
will  serve  to  hold  the  investment  together  during  the  subsequent 
manipulations.   Asbestos  may  be  added,  and  is  a  useful  ingredient 

Fig.  509. 


Fig.  508. 


Burnt  plaster,  or  that  which  has  been  previously  used  for  invest- 
ing, may  be  substituted  for  the  sand  and  asbestos,  adding  a  suf- 
ficient quantity  of  unused  plaster  to  effect  consolidation.  Either 
of  the  combinations  mentioned  will  suffer  but  little  change  in 
the  fire  if  properly  managed.  It  is  customary  to  incase  the  piece 
in  the  plaster  mixture  to  the  depth  of  from  one-half  to  three- 
fourths  of  an  inch,  leaving  only  the  lingual  surfaces  of  the 
plate  and  teeth  uncovered. 

"Warping  or  Springing. — However  comparatively  free    from 


468  MECHANICAL    DENTISTRY. 

change  of  form  the  best  combinations  of  plaster  may  be,  yet 
some  slight  contraction  of  the  body  of  the  investment  doubtless 
ensues  on  the  application  of  heat,  and  it  is  probable  that  so 
large  and  resistant  a  mass  must  tend,  in  some  degree,  to  produce 
deformity  of  the  plate  in  soldering;  for,  as  the  investment  con- 
tracts and  the  plate  at  the  same  time  expands  when  heated,  a 
change  in  the  form  of  the  latter  must  occur  whenever  the  force 
exerted  by  the  shrinking  plaster  exceeds  the  expansive  force  of 
the  metal;  and  when  the  peculiar  form  of  the  upper  plate  is 
considered  we  can  readily  conceive  how  a  slight  contraction  of 
the  plaster  of  the  thickness  mentioned  may  "  warp  "  or  "  spring  " 
the  plate  when  its  uniform  linear  expansion  and  contraction  is 
so  effectively  opposed.  The  change  in  the  form  of  the  base  from 
this  cause  will,  according  to  the  writer's  observations,  be  found, 
in  an  upper  plate,  to  exist  on  each  side  of  the  sloping  walls  of 
the  palate,  embracing  the  posterior  half  or  two-thirds  of  the 
plate  at  these  two  points — the  change  manifesting  itself  in  an 
inward  displacement  of  the  lateral  walls  of  the  plate  midway 
between  the  summit  of  the  palatal  arch  and  the  most  depending 
portion  of  the  ridge.  We  would  suggest  in  explanation  of  this 
result  that,  as  the  plaster  contracts  with  sufficient  force  to  carry 
the  plate  with  it,  the  sides  of  the  latter  are  approximated,  while 
the  palatal  portion  is  at  the  same  time  lifted  up.  Now  it  seems 
plain  that  inasmuch  as  the  portions  of  plate  overlapping  the 
ridge  are  encased  in  and  embraced  by  the  plaster,  and  as  the 
palatal  portion  is  arched  in  form  with  its  convexity  presenting 
to  the  plaster,  and  therefore  self-sustaining  in  respect  to  its  own 
peculiar  form,  the  special  configuration  of  these  parts  cannot 
suffer  any  appreciable  change;  but  as  they  are  forced  toward 
the  common  center  of  the  mass,  their  relation  to  each  other  is 
also  changed,  and  this  changed  relation  must  necessarily  result 
in  a  deformity  of  those  parts  of  the  plate  which  offer  the 
least  resistance  to  the  contractile  force  of  the  plaster.  In  obedi- 
ence to  this  necessity,  the  sides  of  the  plate  along  the  sloping 
walls  of  the  palate,  which  from  their  form  are  neither  resistant 
nor  self-sustaining  under  pressure,  and  whose  inward  displace- 
ment is  unopposed  by  any  counter  force,  are  projected  in  toward 
the  center  of  the  palatal  excavation  in  proportion  as  the  borders 


ENTIRE    DENTURES    ATTACHED    TO    SWAGED    PLATE-BASE.     469 

and  central  portions  are  approximated  or  converged  in  the 
direction  of  the  center  of  the  piece.  The  practical  effect  of  this 
approximation  of  the  lateral  and  posterior  borders  and  internal 
displacement  of  the  plate  is  to  make  the  latter  "  bind  "  upon 
the  outer  and  posterior  borders  of  the  alveolar  ridge,  and  to 
throw  the  central  portion  of  the  plate  from  the  roof  of  the 
mouth. 

Methods  of  Overcoming  the  Tendency  to  Change  in  Form. 
— To  obviate,  as  far  as  practicable,  any  change  in  the  form  of  the 
plate  which  may  result  from  the  contraction  of  the  plaster  invest- 
ment, various  expedients  have  been  suggested,  but  the  following 
will  sufficiently  counteract  the  influence  of  the  plaster  by  per- 
mitting an  unobstructed  expansion  and  contraction  of  the 
metallic  base.  Take  a  band  of  tolerably  thick  copper  plate  as 
wide  as  the  plate  and  teeth  are  deep  ;  bend  it  to  the  form  of  the 
plate,  but  large  enough  to  leave  a  space  of  nearly  half  an  inch 
between  it  and  the  teeth,  the  ends  being  united  to  each  other 
back  of  the  plate  by  riveting  or  otherwise.  Holes  are  then 
made  in  the  band  at  numerous  points  throughout  its  extent, 
through  which  wire  is  introduced  and  interlaced  on  the  inside  in 
such  a  way  as  to  form  loops,  the  latter  extending  in  to  within  a 
short  distance  of  the  teeth.  The  plaster  is  then  filled  into  the 
space  between  the  band  and  teeth,  even  with  the  cutting  and 
grinding  surfaces  of  the  latter  ;  the  palatal  surface  of  the  plate 
is  also  covered  with  plaster  and  maybe  connected  with  the  outer 
portion  by  a  very  thin  layer  at  the  edge  of  the  plate,  or  the  two 
may  be  entirely  disconnected.  The  expansion  of  copper  being 
very  nearly  that  of  gold,  the  body  of  the  plaster,  when  heat  is 
applied,  will  be  carried  in  advance  of  the  borders  of  the  plate  as 
the  latter  expands,  while  the  thin  portion  of  plaster  at  the  edges 
of  the  plate  will  allow  the  central  portion  of  the  latter  to  expand 
with  but  little  or  no  interruption.  On  cooling,  the  entire  mass 
will  contract  and  assume  its  original  form,  unless  warping  is 
induced  by  other  agencies  acting  independently  of  the  envelop- 
ing plaster,  as  excess  or  unequal  distribution  of  solder,  irregular 
heating,  etc. 

It  is  not,  ordinarily,  necessary  to  provide  by  any  special  expe- 
dient against  warping  of  the  lower  plate,  as  any  slight  change  of 


470  MECHANICAL    DENTISTRY. 

form  consequent  on  contraction  will  not  materially  affect  its 
adaptation  to  the  lower  jaw, — its  only  effect  being  to  impart  to 
the  substitute  a  slight  lateral  play  upon  the  ridge.  The  plaster 
on  the  inside  of  the  lower  piece  may  be  cut  away  to  the  edge  of 
the  plate,  while  that  external  to  the  teeth  should  not  be  added 
in  greater  quantities  than  is  barely  sufficient  to  hold  the  latter 
in  place  whilst  lining  and  soldering  them  to  the  base. 

Backing  or  Lining  the  Teeth. — The  plate  being  properly 
invested,  all  portions  of  the  wax  attached  to  the  inner  surface 
of  the  teeth  and  plate  should  be  thoroughly  removed  with 
suitable  instruments,  after  which  stays  or  backings  are  to  be 
adjusted  to  the  teeth.  In  reference  to  the  method  of  forming 
and  adjusting  stays,  little  need  be  added  to  what  has  already 
been  said  when  treating  of  partial  dentures.  One  method,  not 
there  specified,  consists  in  first  fitting  to  each  tooth  separately, 
in  the  usual  manner,  a  thin  stay  formed  of  platinum,  which  is 
temporarily  fastened  to  the  tooth  by  splitting  and  spreading 
apart  the  ends  of  the  rivets  with  a  small  chisel-shaped  instru- 
ment. The  teeth  are  then  removed  from  the  investment  and 
partially  embedded  side  by  side  in  plaster,  the  platinum  strips 
remaining  uncovered.  The  plaster  and  teeth  may  then  be 
raised  to  a  full  red  heat  with  a  blowpipe  or  by  placing  them  in 
the  furnace.  Small  pieces  of  gold'plate,  of  equal  fineness  with 
the  base,  are  then  placed  upon  the  surfaces  of  the  platinum 
stays  and  thoroughly  fused  with  the  blowpipe  until  they  flow 
perfectly  in  around  the  rivets,  and  uniformly  over  the  surface 
of  the  linings.  If  sufficient  heat  is  applied,  the  solder  will 
insinuate  itself  between  the  stay  and  tooth,  and  thus  render  the 
coaptation  of  the  two  perfect.  Small  pieces  of  gold  plate  should 
be  added  until  sufficient  thickness  is  imparted  to  the  linings. 
The  backings  are  then  trimmed  smoothly  and  burnished,  when 
they  may  be  placed  back  in  the  investment  in  their  appropriate 
places.  The  linings  which  support  the  teeth  may  be  united  to 
each  other  laterally  in  sections  or  continuously.  When  the 
teeth  are  joined  to  each  other  throughout,  a  very  small  quantity 
of  solder  will  be  sufficient  to  support  the  teeth,  provided  it  is 
well  diffused  along  the  joints,  uniting  them  perfectly  at  all 
points. 


ENTIRE    DENTURES    ATTACHED    TO    SWAGED    PLATE-BASE.     47 1 

Soldering  and  Finishing. — The  process  of  preparatory  heat- 
ing, soldering,  pickling,  and  finishing  the  plate  is  the  same  in 
all  respects  as  that  described  when  treating  of  partial  pieces,  and 
need  not,  therefore,  be  recapitulated. 

In  the  final  adjustment  of  the  finished  piece  to  the  mouth,  and 
after  any  additional  grinding  of  the  masticating  surfaces  of  the 
teeth  necessary  to  perfect  the  antagonism  has  been  performed, 
such  instructions  should  be  given  to  the  patient  in  regard  to  the 
care  and  management  of  the  appliances  as  will  best  promote 
their  immediate  and  successful  use.  The  wearer  should  be  im- 
pressed with  the  absolute  necessity  of  early  and  prompt  atten- 
tion to  any  injuries  inflicted  upon  the  soft  tissues  of  the  mouth 
by  the  substitutes,  as  much  future  trouble  and  annoyance,  if  not 
permanent  mutilation  of  the  parts,  may  result  from  neglect,  but 
which  may  be  readily  averted,  in  most  instances,  by  a  timely 
removal  of  the  sources  of  injury.  To  obviate,  in  some  measure, 
the  tendency  to  displacement  of  the  base,  which  usually  accom- 
panies the  first  use  of  artificial  teeth,  and  especially  the  upper 
denture,  the  patient  maybe  directed,  when  dividingfood  with  the 
front  teeth,  to  press  the  substance  backward  and  upward  against 
the  cutting  edges  of  the  superior  incisors  at  the  same  time  that 
the  opposing  teeth  are  closed  upon  each  other,  thus  dividing 
completely  the  substance  seized.  In  reference  to  the  mastication 
of  food,  it  has  been  suggested  to  instruct  the  patient  to  distribute, 
by  the  action  of  the  tongue,  the  portions  of  food  as  equally  as 
possible  on  each  side  of  the  mouth,  in  this  manner  distributing 
the  forces  applied,  and  thereby  lessening  the  chances  of  lateral 
displacement  of  the  substitute. 


CHAPTER  XI. 
MANUFACTURE  OF   PORCELAIN  TEETH. 

The  perfection  and  completeness  of  results  attained  at  this 
day  in  the  production  of  porcelain  teeth,  approximating  so 
nearly  the  natural  organs  in  all  their  more  obvious,  physical, 
and  distinctive  characteristics  as  to  be  almost,  if  not  quite, 
indistinguishable  from  the  latter  when  applied  in  obedience  to 
the  esthetic  requirements  of  individual  cases,  is  one  of  the  mar- 
vels of  ceramic  art.  Nowhere,  perhaps,  have  the  conceptions  of 
genius  been  embodied  in  porcelain  with  more  truthfulness  or 
greater  fidelity  to  nature  than  in  the  exquisite  and  wonderful 
imitations  of  the  dental  manufacturing  laboratory. 

So  amply  and  satisfactorily  has  the  intelligent,  progressive, 
and  well-directed  enterprise  of  manufacturers  provided  for  all 
the  ordinary  needs  of  prosthetic  practice  in  the  almost  endless 
variety  in  size,  color,  configuration,  relation,  and  adaptability  of 
single  and  sectional  teeth,  that  the  work  of  hand-carving  is  now 
rarely  demanded  of  the  general  practitioner  except  in  extreme 
cases  resulting  either  from  accident  or  disease.  Thus,  as  aptly 
remarked  by  the  late  Professor  Austen  :  "  The  dental  depot  not 
only  renders  service  by  the  superior  excellence  of  the  surgical 
instruments  and  prosthetic  materials  which  it  supplies,  but  it 
directly  benefits  the  science  and  art  of  dentistry  by  releasing 
the  practitioner  from  manufacturing  toil,  and  giving  time  for 
the  acquirement  of  increased  knowledge  and  skill.  Thus,  if  the 
time  heretofore  given  to  block-making  were  devoted  to  the 
study  of  dental  esthetics,  patients  would  have  the  benefit  of  an 
artistic  selection  from  a  far  larger  variety  of  porcelain  dentures 
than  could  otherwise  possibly  be  made." 

As  affording  some  'curious  as  well  as  practical  information  in 
regard  to  the  composition  and  manufacture  of  porcelain  teeth, 
the  following  descriptions  will  be  found  of  interest : — 

472 


MANUFACTURE    OF    PORCELAIN    TEETH.  473 

Components  of  Dental  Porcelain, — Manufactured  single 
and  sectional  mineral  teeth,  carved  block-teeth,  continuous-gum 
material,  etc.,  are  composed  of  two  distinct  portions, — the  body, 
or  base,  and  ena)ncl.  The  chief  mineral  substances  which  com- 
pose the  body  are  silex,  felspar,  and  kaolin.  The  enamel,  both 
crown  and  gum,  consists  principally  oi  felspar. 

The  various  tints  or  shades  are  imparted  to  the  porcelain  by 
certain  metals  in  a  state  of  minute  division  or  their  oxids.  The 
more  general  properties  of  the  mineral  ingredients  will  be  first 
described. 

Silex. — Silex,  silica,  or  silicic  acid,  is  a  white  powder,  inodor- 
ous, and  insipid.  It  forms  the  chief  part  of  many  familiar 
mineral  formations,  as  quartz,  rock-crystal,  flint,  agate,  and 
most  sands  and  sandstones,  in  some  of  which  it  occurs 
nearly  pure.  Silica,  in  its  pure  state,  is  insoluble  in  water  or 
acids,  and  is  infusible  in  the  highest  heat  of  the  furnace  ;  it 
melts,  however,  in  the  flame  of  the  oxyhydrogen  blowpipe, 
passing  into  a  transparent,  colorless  glass.  Its  specific  gravity 
is  2.66  ;  and  it  is  composed  of  silicon,  48.04,  and  oxygen,  51.96. 
Only  the  purest  varieties  of  silex  are  employed  in  the  manu- 
facture of  porcelain  teeth.  It  is  prepared  for  use  by  subjecting 
it  to  a  white  heat  and  then  plunging  it  into  cold  water,  after 
which  it  is  ground  to  a  very  fine  powder  in  a  mortar. 

Felspar. — This  mineral  substance  occurs  crystallized  in 
oblique  rhomboidal  prisms,  and  is  a  constant  ingredient  of 
granite,  trachyte,  porphyry,  and  many  of  the  volcanic  rocks. 
The  felspathic  mineral  formations  present  either  a  pearly  or 
vitreous  luster,  and  vary  in  color,  being  red,  green,  gray, 
yellow,  brown,  flesh-colored,  pure  white,  milky,  transparent,  or 
translucent.  Felspar  yields  no  water  when  calcined ;  melts  at 
the  blowpipe  into  a  white  enamel,  and  is  unaffected  by  acids. 
It  is  composed,  according  to  Rose,  of  silica,  66.75  ;  alumina, 
17.50;  potash,  12;  lime,  125;  oxid  of  iron,  0.75.  It  is  found 
in  various  localities  throughout  the  United  States,  the  purest 
and  whitest  kinds  being  employed  in  the  manufacture  of 
mineral  teeth.  It  is  prepared  for  use  in  the  same  manner  as 
silex. 

Felspar,  from    its  ready  fusibility,  serves   to  agglutinate  the 


474  MECHANICAL    DENTISTRY. 

particles  of  the  more  refractory  ingredients,  silex  and  kaolin  ; 
and  when  diffused  throughout  the  mass  imparts  to  the  porcelain 
a  semi-translucent  appearance. 

Kaolin. — Kaolin,  or  decomposed  felspar,  is  a  fine  white  variety 
of  clay,  and  is  composed  chiefly  of  silica  and  alumina,  the  latter 
being  the  characteristic  ingredient  of  common  clay.  It  is  found 
in  various  localities  throughout  the  Eastern  States  and  in  parts  of 
Asia  and  Europe.  Kaolin  is  refractory,  or  fire-proof,  but  is 
rendered  more  or  less  fusible  by  the  contaminations  of  iron  and 
lime  with  which  it  is  usually  combined.  The  opaque  and  life- 
less appearance  characteristic  of  the  earlier  manufacture  of 
mineral  teeth  was  due  to  the  introduction  of  a  relatively  large 
proportion  of  this  clay  into  the  body  of  the  porcelain.  The 
peculiar  translucent  and  lifelike  expression  which  distinguishes 
the  beautiful  imitations  of  the  present  day  is  due,  in  great  part, 
to  the  comparatively  small  proportion  of  kaolin  clay,  and  an 
increased  amount  of  the  more  fusible  and  vitreous  component, 
felspar. 

Kaolin  is  prepared  for  use  by  washing  it  in  clean  water ;  the 
coarser  particles  having  settled  to  the  bottom,  the  water  holding 
the  finer  ones  in  solution  is  poured  off,  and  when  the  suspended 
clay  is  deposited  at  the  bottom  of  the  vessel,  the  water  is  again 
poured  off,  and  the  remaining  kaolin  dried  in  the  sun. 

Coloring  Materials. — The  following  metals  and  oxids  are 
employed  in  coloring  mineral  teeth :  titanium,  platina  sponge, 
and  oxid  of  gold  being  those  chiefly  used  in  producing  the 
more  positive  tints,  and  by  combining  which,  in  varying  propor- 
tions, any  desired  shade  or  color  may  be  obtained. 

METALS   AND   OXIDS.  COLORS   PRODUCED. 

Gold  in  a  State  of  minute  .division,  ^^>- Rose  red. 

Oxid  of  gold, •  .    .    .  Bright  rose  red. 

Platina  sponge  and  fillings, Grayish- blue. 

Oxid  of  titanium, Bright  yellow. 

Purple  of  Cassius,      Rose  purple. 

Oxid  of  uranium, Greenish-yellow. 

Oxid  of  manganese, Purple. 

Oxid  of  cobalt, Bright  blue. 

Oxid  of  silver, Lemon  yellow. 

Oxid  of  zinc, Lemon  yellow. 


MANUFACTURE    OF    PORCELAIN    TEETH.  475 

As  the  preparation  of  most  of  the  above  colors  requires  great 
care  and  a  somewhat  intimate  knowledge  of  chemistry,  and  as 
the  most  delicate  manipulations  are  necessary  to  secure  accu- 
rate and  satisfactory  results,  it  is  better  for  the  mechanical  oper- 
ator to  procure  the  coloring  ingredients  already  prepared  from 
some  competent  chemist,  rather  than  attempt  their  production 
himself.  For  a  particular  description  of  the  various  modes  of 
preparing  them,  the  reader  is  referred  to  Piggot's  Dental  Cliemistry 
and  Mctalhirgy,  and  other  works  treating  fully  of  the  subject. 

Manufacture  of  Porcelain  Teeth. — The  subjoined  account 
of  the  processes  concerned  in  the  manufacture  of  porcelain  teeth 
is  descriptive  of  those  at  present  employed  by  most  of  our  lead- 
ing manufacturers. 

The  felspar  is  first  calcined  by  throwing  it  in  large  masses  into 
a  furnace,  and  subjecting  it  to  a  red  heat  and  then  plunging  it 
into  water,  which  renders  it  brittle  and  easily  broken  by  the 
hammer  into  small  pieces,  so  that  all  foreign  matters,  such  as 
mica  or  iron,  with  which  it  may  be  mixed,  can  be  separated.  It 
is  then  crushed  between  flint  stones,  and  when  fine  enough  is 
afterward  ground  under  water  in  a  mill  in  which  heavy  blocks 
of  French  bur-stone  revolve  upon  a  nether  millstone  of  the  same 
material,  until  sufficiently  pulverized,  when  it  is  floated  off  and 
allowed  to  settle.  After  this  the  water  is  drawn  off  or  evaporated, 
and  the  deposit  of  spar  dried  and  sifted. 

The  silex  is  subjected  to  the  same  treatment. 

The  kaolin,  already  of  the  desired  consistency  as  found  in 
nature,  is  prepared  for  use  by  first  washing  out  impurities,  and 
then  drying. 

The  mineral  ingredients  are  ground  somewhat  coarsely,  but 
the  coloring  materials  are  reduced  to  an  impalpable  powder  by 
means  of  a  mortar  and  pestle  machine  of  great  power. 

When  properly  prepared,  the  several  materials  are  combined 
in  suitable  proportions  to  form  the  body  and  enamels,  and  are 
then  mixed  with  water  and  worked  into  masses  of  the  required 
consistency  for  molding.  The  degree  of  plasticity  of  the  body 
and  enamel  pastes  differs  with  the  methods  of  manufacture. 
Formerly,  the  teeth,  when  molded,  were  first  exposed  to  a  heat 
just  sufficient  to  produce  partial  baking  of  the  body,  and  this  was 


476  MECHANICAL    DENTISTRY. 

called  cruising  or  bisaiiting,  after  which  a  thin  paste  of  enamel 
material  was  applied  with  a  camel's-hair  brush,  and  the  whole 
subjected  to  a  second  heat  for  complete  and  final  fusion.  This 
preliminary  process  of  biscuiting  is  essential  in  carved  block  and 
continuous-gum  work,  but  in  most  of  the  factories  this  partial 
baking  is  dispensed  with,  and  the  body  and  enamel  pastes  of  the 
uniform  consistency  of  putty  are  introduced  into  the  molds,  in 
the  first  instance,  properly  distributed,  and  final  fusion  effected 
by  a  single  exposure  to  heat. 

The  molds  are  made  of  brass  and  are  in  two  sections,  one-half 
of  the  tooth  being  represented  on  either  side.  The  exact  form  of 
the  tooth  is  carved  out  with  great  care  and  precision,  and  must 
be  anatomically  correct  and  mechanically  perfect,  while  the 
matrix  is  made  about  one-fifth  larger  than  the  required  size  to 
compensate  for  shrinkage  of  the  materials  in  baking.  Holes 
are  drilled  in  each  half  of  the  mold  to  receive  the  platinum  pins, 
and  the  exact  closure  of  the  two  pieces  of  the  mold  secured  by 
guiding  pins. 

The  molds  having  been  previously  oiled,  and  the  platinum 
pins,  which  vary  in  length  and  thickness  to  meet  special  require- 
ments, placed  with  small  tweezers  in  the  holes  provided  for 
them,  the  crown  and  gum  enamels  are  first  carefully  laid  in  with 
small  steel  spatulas  in  the  required  quantity  and  position.  The 
body  is  then  added,  in  quantity  exceeding  somewhat  the  capac- 
ity of  the  mold,  when  the  sections  of  the  mold  are  closed  upon 
each  other  and  subjected  to  a  pressure  sufficient  to  insure  com- 
pactness of  the  enclosed  mass.  When  thoroughly  dried  by  a 
slow  heat,  to  which  the  molds  are  exposed,  the  teeth  are  readily 
disengaged  when  the  matri.x  is  separated,  and  will  be  found  at 
this  stage  extremely  friable  and  tender,  requiring  great  care  in 
handling  them. 

They  are  then  sent  from  the  molding  to  the  trimmer's  room, 
where,  after  critical  inspection,  all  defective  ones  are  either 
repaired  or  condemned,  all  excess  of  material  cut  smoothly 
away,  and  the  arch  of  the  gum  over  each  tooth  made  true  and 
smooth  with  fine,  pointed  instruments.  They  are  then  placed 
on  beds  of  coarse  quartz  sand,  on  fire-clay  trays  or  slides  ready 
for  the  furnace. 


MANUFACTURE    OF    PORCELAIN    TEETH.  4// 

Referring  to  this  stage  in  the  process  of  manufacture,  an 
intelligent  observer  writes  : — 

"  Beyond  this  no  tool  can  follow  them.  Imperfections  here- 
tofore could  be  repaired,  but  in  the  future,  beyond  the  fire,  the 
tooth  is  either  perfect  or  a  failure  irremediable.  The  furnace  is 
an  institution  entitled  to  respect  for  its  intensity.  In  its  center 
is  a  muffle  of  fire-clay,  entirely  surrounded  by  the  glowing  fuel, 
a  charge  of  half  a  ton's  weight  of  coal,  itself  carefully  bricked 
up  before  firing,  that  no  impurities  of  dust  or  vapor  shall  reach 
the  teeth.  Take  out  the  small,  half-oval  door  of  the  muffle  and 
you  will  see  an  inner  glow  the  eye  shrinks  from  registering,  an 
incandescence  that  startles  you  by  its  fervor.  In  from  fifteen  to 
thirty  minutes,  teeth  and  fire-clay  slide,  glowing  like  the  oven, 
are  taken  out  finished.  The  dull  enamel  has  become  as  glass. 
The  lusterless  oxids  have  yielded  their  color,  and  the  tooth 
that  went  in  friable  and  brittle  has  come  out  adamant.  But 
there  is  an  intermediate  skill,  the  acquisition  of  which  is  one 
of  the  marvels  of  the  mechanic  arts.  A  little  too  long  in  that 
heat  and  the  teeth  are  ruined,  and  the  evils  of  'underdone'  are 
equally  to  be  guarded  against.  It  is  a  trained  judgment,  a  skill 
of  eye  and  handling  that  enables  the  burner  to  lend  success  to 
the  work  of  those  who  have  gone  before  him,  and  at  the  precise 
point  where  a  shade  of  failure  is  utter  ruin." 

The  teeth  are  now  done  and  ready  for  the  wax  cards,  on 
which  they  go  to  the  trade. 


CHAPTER  XII. 

UNITING  SINGLE  PORCELAIN  TEETH  TO  EACH  OTHER  AND 
TO  A  METALLIC  BASE  WITH  A  FUSIBLE  SILICIOUS  COM- 
POUND, FORMING  A  CONTINUOUS  ARTIFICIAL  GUM.* 

("  CONTINUOUS-GUM    WORK.") 

The  process  of  uniting  single  mineral  teeth  to  each  other  and 
to  a  metallic  base  by  means  of  a  porcelain  cement  was  attempted 
as  early  as  1820,  by  Delabarre,  of  Paris,  France,  but  with  such 
imperfect  and  unsatisfactory  results  as  induced  its  early  aban- 
donment. At  a  later  period,  Dr.  John  Allen,  a  distinguished 
practitioner  of  dentistry  in  America,  devised  a  method  embrac- 
ing original  and  important  modifications  of  practice  both  in  the 
preparation  and  combination  of  materials,  and  the  modes  of 
manipulating  them  ;  and  after  an  extended  series  of  experiments, 
commencing  in  1844,  succeeded  in  obtaining  certain  mineral 
compounds  which  vitrified  at  a  heat  much  below  that  employed 
by  Delabarre,  and  the  contraction  of  which  corresponded  so  nearly 
with  that  of  the  platinum  base  to  which  it  was  applied  that  the 
shrinkage  incident  to  baking  conflicted  in  no  material  degree 
with  the  practical  utility  of  the  work  in  the  mouth. 

*The  attentive  reader  of  the  first  edition  of  this  work  will  not  fail  to  note  that  the 
statements  involving  the  question  oi  priority,  contained  in  the  introductory  portion  of 
the  above  chapter,  are  at  variance  with  those  originally  published.  A  more  extended 
examination  and  careful  analysis  of  the  evidences  as  they  appear  upon  record — 
evidences  not  fully  accessible  to  the  author  at  the  time  of  the  publication  of  the  first 
edition — established  beyond  reasonable  doubt  the  just  claims  of  Dr.  Allen  as  the 
originator  of  that  special  and  distinctive  method  here  considered,  by  which  the 
attachment  of  the  teeth  to  the  plate  is  effected  by  direct  fusion  of  the  gum  material. 
Dr.  Hunter's  earliest  and  contemporaneous  experiments  contemplated  simply  a  union 
of  all  the  teeth  by  means  of  a  fusible  cement,  forming  a  single,  continuous  block, 
which  was  afterward  united  to  the  base  by  riveting  or  soldering. 

This  brief  explanation  is  here  introduced  as  an  act  of  simple  justice  to  the  late  Dr. 
Allen,  who  devoted  the  best  energies  of  his  life  to  the  successful  development  of  a 
process  which  stands  unrivaled  in  all  the  chief  requisites  of  an  artificial  denture. 

478 


DENTURES    WITH    CONTINUOUS    PORCELAIN    GUM.  479 

In  the  construction  of  dentures  upon  this  principle,  plain  single 
teeth,  made  for  the  purpose,  are  arranged  and  soldered  to  a  plate 
properly  fitted  to  the  mouth,  after  which  different  mineral  com- 
pounds, made  to  represent  the  natural  gum  tissues,  etc.,  are 
applied  to  the  plate  and  teeth  in  a'  plastic  state,  then  carved  and 
trimmed  in  proper  form,  and  by  means  of  a  strong  furnace  heat 
these  compounds,  called  the  body  and  the  gum  enamel,  are 
fused,  producing  a  continuous  and  seamless  artificial  gum  and 
palate  indistinguishable  from  the  natural  structures. 

The  compounds  at  present  employed  in  this  process,  as  well 
as  the  more  fusible  preparations  used  for  repairing  purposes,  are 
manufactured  in  quantities  sufficient  to  meet  the  wants  of  the 
profession,  and  may  be  procured  at  all  the  dental  furnishing 
houses  throughout  the  United  States. 

The  intimate  but  later  identification  of  Dr.  W.  M.  Hunter  with 
the  above  process  has  rendered  his  name  familiar  as  one  whose 
skill  and  devotion  to  this  specialty  of  mechanical  practice  has 
contributed  to  its  development  in  a  modified  form.  Dr.  Hunter's 
formulas  and  modes  of  manipulating  his  compounds  will  be 
introduced  hereafter. 

Following  Dr.  Hunter's  descriptions,  the  reader  will  find  prac- 
tical and  valuable  instructions  in  this  method  of  substitution, 
contributed,  at  the  solicitation  of  the  author,  by  Dr.  S.  P.  Has- 
kell, of  Chicago,  111.,  Professor  George  S.  Field,  of  Detroit, 
Mich.,  and  Dr.  Ambler  Tees,  of  Philadelphia,  Pa.,  whose  long 
experience  and  intimate  familiarity  with  the  most  approved 
methods  of  constructing  continuous-gum  dentures  impart  special 
value  to  the  subject-matter  of  their  communications. 

Before  introducing  an  account  of  Dr.  Allen's  modes  of  pro- 
cedure, we  would  premise  that  it  is  unnecessary  to  repeat  in 
this  connection  what  has  already  been  fully  described  in  regard 
to  impressions  of  the  mouth,  or  the  manipulations  connected 
with  the  formation  of  plaster  models  and  metallic  swages,  these 
processes  being  essentially  the  same  as  in  the  construction  of 
ordinary  gold  work. 

Dr.  C.  H.  Land,  of  Detroit,  Michigan,  has  devised  an  inge- 
nious method  of  attachment. 

The  improvement,  in  its  application  to  continuous-gum  work, 


48o 


MECHANICAL    DENTISTRY. 


is  in  the  construction  of  the  teeth,  which  are  provided  with  three 
pins  arranged  transversely  in  the  cervical  portion  of  the  tooth, — 
one  in  the  center,  and  one  upon  either  side  on  the  posterior 
lateral  aspect  of  the  cervix,  the  latter  being  somewhat  longer 
than  the  center  pin.  The  long  pins  at  the  sides  are  so  arranged 
that,  when  the  teeth  are  in  position,  the  lateral  pins  of  all  the 
teeth  will  cross  each  other,  as  shown  in  Fig.  510.  The  pins  so 
crossed,  and  also  the  center  pins,  are  pressed  down  closely  upon 
the  plate,  and  the  whole  united  to  each  other  and  to  the  base  by 
flowing  solder  at  the  points  where  they  cross,  and  at  their  line 
of  junction  with  the  base. 

These  teeth  are  designed  more  especially  for  continuous-gum 
work,  but  are  applicable  to  dentures  attached  to  gold  plates  by 


Fig.  510. 


rubber  or  celluloid,  and  may  be  used  also  to  advantage,  in  a 
modified  form,  in  the  use  of  rubber  or  celluloid  alone. 

The  particular  advantages  claimed  for  these  teeth  are,  that  in 
their  use  in  continuous-gum  cases,  equal  or  greater  strength  is 
imparted  to  a  plate  made  much  thinner  than  those  ordinarily 
employed,  say  32  to  33  Stub's  gauge,  thus  materially  reducing 
the  weight  of  the  piece,  while  at  the  same  time  they  offer  greater 
facility  and  certainty  in  the  manipulation  of  the  gum  body. 

It  may  also  be  premised,  before  considering  individual 
methods,  that  it  has  not  been  deemed  necessary  to  encumber  a 
description  of  these  processes  by  illustrations  of  the  different 
kinds  of  furnaces  used  for  the  purpose.  These  have  been  fully 
represented  under  the  head  of  "  Furnaces." 


DENTURES    WITH    CONTINUOUS    PORCELAIN    GUM.  48 1 

Dr.  Allen's  Methods. — The  following  descriptions  embrace 
the  methods  and  manipulations  practised  by  the  late  Dr.  John 
Allen  in  the  construction  of  artificial  dentures  with  continuous 
gums. 

The  plate  or  base  is  formed  of  platinum,  or  platinum  and 
iridium.  The  plate  being  properly  fitted  to  the  mouth,  and  wax 
placed  upon  it  for  the  bite,  as  in  ordinary  plate  work,  the  teeth 
are  arranged  thereon  with  special  reference  to  the  requirements 
of  the  case.  They  are  then  covered  with  a  thin  coating  of 
plaster  mixed  with  water  to  the  consistency  of  cream.  After 
this  has  become  firmly  set,  another  mixture  of  plaster  and  as- 
bestos with  water,  somewhat  thicker  or  more  plastic  than  the 
first,  is  placed  round  on  the  outside  of  the  previous  covering  and 
the  plate.  A  convenient  way  of  applying  the  second  covering 
is  to  turn  the  mixture  out  of  the  vessel  upon  a  piece  of  tin,  say 
four  or  five  inches  square,  thus  forming  a  cone,  upon  which  the 
plate,  with  the  teeth  upward,  is  pressed  gently  down  until  within 
an  inch  or  less  from  the  tin.  Then  with  a  spatula  the  mixture  is 
brought  up  over  the  teeth,  forming  an  investment  that  will  not 
crack  in  the  process  of  soldering.  Sand  may  be  used  with  the 
plaster  for  this  purpose,  but  I  think  asbestos  preferable. 

Attaching  the  Teeth. — When  the  covering  has  become 
sufficiently  hard,  the  wax  is  removed,  and  a  rim  of  platinum  is 
then  fitted  to  the  lingual  side  of  the  teeth,  below  the  pins,  and 
to  the  base-plate.  The  pins  in  the  teeth  are  then  bent  down 
upon  the  rim,  and  soldered  with  pure  gold,  or  a  mixture  of  gold 
and  platinum,  at  the  same  time  the  rim  is  soldered  to  the  plate. 
This  rim,  which  forms  the  lining  for  the  teeth,  is  usually  about 
the  thickness  of  the  plate  upon  which  they  are  set,  say  twenty- 
eight  to  thirty ;  but  should  the  case  require  more  than  ordinary 
strength,  a  double  or  triple  thickness  of  rim  should  be  used. 
This  may  become  necessary  in  cases  where  the  natural  molar 
teeth  are  standing  firmly  in  the  opposite  jaw,  and  antagonize  with 
the  artificial  piece,  or  where  from  any  cause  an  undue  strain  is 
brought  to  bear  upon  the  artificial  teeth.  To  attain  successful 
results,  the  dentist  must  take  into  consideration  all  the  circum- 
stances or  conditions  of  each  particular  case,  and  then  exercise 
his  best  judgment  in  executing  the  work. 
31 


482  MECHANICAL    DENTISTRY. 

In  soldering  platinum  with  pure  gold,  flat  surfaces  of  this 
metal  should  be  brought  in  positive  contact,  in  order  to  become 
firmly  united.  Therefore  in  mounting  teeth  upon  a  plate  of  this 
kind  the  backing  or  inside  rim  should  be  a  little  wider  than  the 
distance  between  the  pins  in  the  teeth  and  the  plate,  say  from  an 
eighth  to  a  fourth  of  an  inch.  This  extra  width  of  rim  should 
be  bent  at  right  angles  along  the  base  of  the  teeth,  so  as  to 
admit  of  being  pressed  down  upon  the  plate  after  the  rim  is 
adjusted  to  the  teeth,  and  the  pins  bent  down  firmly  upon  it. 
In  this  way  flat  surfaces  of  the  rim  and  plate  are  brought  to- 
gether and  soldered.  The  pins  in  the  teeth  are  also  soldered  to 
the  rim  at  the  same  time.  When  the  parts  are  thus  united,  they 
will  remain  so  during  the  subsequent  bakings;  but  if  the  edge 
of  the  rim  only  is  fitted  to  the  plate  and  soldered  like  gold  or 
silver  work,  the  subsequent  heatings  for  baking  the  body  and 
gum  will  cause  the  gold  to  become  absorbed  in  the  platinum, 
and  leave  the  joints  not  united.  It  may  be  asked,  Why  not  use 
common  gold  solder  for  this  style  of  work  ?  Answer,  because 
the  alloy  in  the  solder  will  greatly  injure  the  color  of  the  gum 
enamel  in  baking.  Copper  alloy  will  turn  it  to  a  greenish  shade, 
and  silver  will  give  it  a  yellow  tinge.  Although  pure  gold  re- 
quires more  intense  heat  to  melt  it  (being  about  two  thousand 
degrees)  than  ordinary  gold  solder,  yet  when  melted  it  flows 
much  more  freely  than  the  latter.  The  best  way  to  solder  the 
teeth  upon  platinum  plate  is  to  place  small  pieces  of  gold  upon 
the  joints  or  parts  to  be  soldered,  with  wet  ground  borax,  and 
then  slowly  introduce  the  piece  with  the  investment  into  a  heated 
muffle,  and  bring  the  whole  mass  up  to  a  red  heat ;  then  with- 
draw it  from  the  furnace,  and  bring  it  quickly  under  the  blow- 
pipe to  flow  the  gold.  In  this  way  the  teeth  do  not  become 
etched,  as  they  are  liable  to  be  if  the  soldering  is  done  in  the 
furnace. 

The  piece  being  soldered  and  cooled,  the  covering  is 
removed  from  the  teeth,  taking  care  to  preserve  the  base 
unbroken  for  the  plate  to  sit  upon  during  the  subsequent 
bakings  of  the  body  and  gum  enamel. 

Preparing  and  Applying  the  Body. — All  particles  of  plaster 
or   other    foreifjn    matter  should   be    removed    from    the    teeth 


DENTURES  WITH  CONTINUOUS  PORCELAIN  GUM. 


483 


and  plate  by  thoroughly  washing  and  brushing  them.  It  is 
well  to  immerse  the  piece  for  a  short  time  in  sulphuric  acid, 
after  which  rinse  and  brush  it  well  with  water.  This  done,  a 
colorless  mineral  compound,  called  the  body,  is  applied  in  a 
plastic  state  (with  spatulas  or  small  instruments  for  the  purpose) 
to  the  teeth  and  plate.  It  is  then  carved  to  represent  the  gum, 
roof,  and  rugae  of  the  mouth,  taking  care  to  keep  the  crowns  of 
the  teeth  well  defined.  Small,  clean  cuts  with  a  thin  knife  blade 
should  then  be  made,  one  between  each  of  the  teeth.  Com- 
mencing with  the  space  between  the  molars,  the  cuts  should  be 
made  externally  and  internally  entirely  through  the  body  to 
the  stay  and  the  plate.     The  object  of  these  separations  is  to 


Fk;.    :;ii. 


Fig.   S12. 


prevent  movement  on  the  part  ot  the  teeth  from  contraction  of 
the  body  in  baking,  compelling  the  material  to  shrink  toward 
the  teeth  and  unite  with  them,  leaving  smooth  and  irregular 
openings  where  the  incisions  were  made,  into  which  more 
material  is  readily  introduced  and  baked.  Fig.  511  shows  a 
case  after  the  first  heating. 

First  Baking. — The  piece  is  then  placed  on  the  base  upon 
which  it  was  soldered,  and  set  upon  a  slide  on  the  apron  in 
front  of  one  of  the  upper  muffles  of  the  heated  furnace, — and 
every  eight  or  ten  minutes  it  should  be  moved  forward  into  the 
muffle,  say  two  or  three  inches  each  time,  until  the  piece  shall 


4^4  MECHANICAL    DENTISTRY. 

have  passed  the  center  of  the  same,  which  should  be  at  a  red 
heat.  It  is  then  withdrawn  and  passed  into  a  lower  muffle, 
where  the  heat  is  greater,  in  which  the  body  soon  becomes 
semi-vitrified,  which  is  sufficient  for  the  first  bake.  It  is  then 
taken  out  and  (together  with  the  slide  on  which  it  was  baked) 
placed  in  a  cooling  muffle,  the  mouth  of  which  should  be  closed 
to  prevent  the  change  of  temperature  from  being  too  rapid  and 
causing  the  teeth  to  become  brittle.  When  the  piece  is  suffi- 
ciently cool  to  handle,  a  second  application  of  body  is  made  for 
the  purpose  of  repairing  any  defects  that  may  have  occurred  in 
the  baking;  this  done,  the  piece  is  again  introduced  as  before 
into  the  upper  muffle,  then  in  the  lower,  allowing  the  second 
bake  to  become  a  little  harder  than  the  first,  but  not  so  much  as 
to  appear  glossy.  It  is  then  withdrawn,  and  cooled  as  de- 
scribed above. 

Applying  the  Gum  Enamel. — A  flesh-colored  compound  is 
then  applied,  which  is  called  the  gum  enamel.  This  is  also 
made  plastic  with  water,  and  a  thin  coating  is  put  over  the  body 
and  closely  packed  and  carved  around  the  teeth  with  small 
instruments  made  for  the  purpose, — still  taking  care  to  keep  the 
crowns  of  the  teeth  clean  and  well  defined.  Small  camel's-hair 
brushes  are  used  wet  with  water  to  cause  the  gum  enamel,  and 
also  the  body,  to  settle  more  closely  around  the  necks  of  the 
teeth  ;  other  brushes  are  also  used  dry  to  remove  all  particles 
of  body,  gum,  or  other  substances  from  the  crowns  of  the  teeth. 

Final  Baking. — After  the  application  of  the  gum  enamel, 
the  piece  is  again  subjected  to  the  heat  of  the  furnace  as 
described  for  baking  the  body,  with  this  difference:  The  heat 
should  be  a  little  greater  than  for  either  of  the  preceding 
bakes.  It  should  be  a  strong,  sharp  heat,  in  order  to  produce  a 
smooth,  glossy  appearance,  which  is  required  for  the  enamel. 
These  different  degrees  of  heat  for  the  first,  second,  and  third 
baking  should  be  carefully  observed  for  the  purpose  of  getting 
an  even  temper  in  the  piece,  and  thereby  preventing  it  from 
crazing  or  cracking  in  cooling. 

The  enamel  being  thoroughly  fused,  the  piece  is  withdrawn 
from  the  heated  muffle,  and  passed  into  another,  outside  of  the 
furnace.     This   muffle    should   be   made   quite   hot    before  the 


DENTURES    WITH    CONTINUOUS    PORCELAIN    GUM.  485 

denture  is  placed  in  it,  in  order  to  prolong  the  cooling  process  ; 
for  if  the  piece  is  cooled  too  rapidly  it  is  rendered  more  fragile. 
It  is  well  to  let  the  case  remain  in  the  cooling  muffle,  with  the 
mouth  of  it  closed,  several  hours  before  exposing  it  to  the  air. 
By  baking  just  at  night  the  piece  will  be  in  proper  condition  to 
finish  up  the  next  morning.  Fig.  512  shows  the  case  com- 
pleted. 

The  Finishing  Process  consists  simply  in  smoothing  and 
polishing  the  plate  and  burnishing  the  rim.  It  is  then  ready  to 
be  adjusted  to  the  mouth.  In  baking  great  care  is  necessary 
to  prevent  the  piece  from  becoming  gassed.  This  can  be 
avoided  by  allowing  the  gas  to  escape  entirely  from  the  burning 
coal  or  coke  in  the  furnace  before  the  piece  is  introduced  into 
the  muffle.  The  presence  of  gas  is  indicated  by  the  blue  flame 
escaping  from  the  coal.  When  the  fire  becomes  clear,  it  is  then 
safe  to  introduce  the  case  to  be  baked  (as  before  described)  into 
the  muffle.  Pure  anthracite  coal  is  the  best  for  this  purpose,  as 
it  maintains  a  longer  and  stronger  heat  than  coke.  Bituminous 
coal  is  not  good  for  this  kind  of  work  unless  first  converted  into 
coke. 

It  often  occurs  that  the  natural  gums  will  change  more  or 
less  after  the  teeth  are  inserted.  In  such  cases  a  new  impression 
should  be  taken  from  the  mouth  and  a  fusible  die  formed.  The 
denture  is  then  placed  upon  the  die,  and  it  will  be  seen  at  once 
where  the  change  has  taken  place  ;  then  with  the  piece  resting 
upon  the  die  the  artificial  gum  may  be  chipped  off  with  a  small 
hammer  and  chisel.  The  platinum  plate,  being  soft,  can  be 
refitted  to  the  die  very  accurately  with  a  burnisher,  hammer,  and 
small  driver  made  for  the  purpose.  A  new  coat  of  body  is  then 
applied  where  the  plate  has  been  refitted,  and  then  baked,  cooled, 
enameled,  and  baked  again, — still  observing  the  same  directions 
as  detailed  in  the  management  of  new  pieces. 

Repairing. — If  the  tooth  gets  broken  (a  mishap  which 
seldom  occurs  by  use  in  the  mouth)  it  can  be  replaced  with 
another  by  grinding  out  the  remaining  portion  of  the  broken 
tooth,  and  the  gum  which  covers  the  fang,  and  then  fitting  a  new 
one  in  the  place.  This  tooth  need  not  be  soldered  to  the  inside 
rim  ;  it  is  sufficient  to  grind   a  small  notch   or  groove  in  the 


486  MECHANICAL    DENTISTRY, 

enamel  which  covers  the  lingual  side  of  the  rim  for  the  pin  of 
the  tooth  to  fit  into.  The  pin  resting  in  the  groove  is  covered 
with  the  body  at  the  same  time  it  is  applied  around  the  base  of 
the  tooth,  and  when  this  body  is  baked  the  tooth  will  become 
firmly  fastened  in  place  of  the  broken  one.  Any  number  of 
teeth  that  may  be  required  can  be  replaced  in  this  way.  If  it 
is  desired  to  change  the  position  of  one  or  more  teeth,  or  to 
make  them  longer,  this  can  also  be  done  as  described  above, 
with  the  additional  precaution,  to  press  softened  wax  upon 
the  inside  of  the  teeth  and  palatal  arch  of  the  denture  before 
the  others  are  removed, — this  wax  will  serve  as  a  guide  or 
index  as  to  the  relative  change  to  be  made,  and  also  to  sustain 
the  teeth  in  place  while  they  are  being  fitted  as  desired  to 
the  denture.  The  wax  soon  becomes  hard,  and  is  readily 
removed  as  each  successive  tooth  is  ground  and  adjusted  in  its 
proper  place. 

When  the  teeth  are  thus  fitted  with  each  pin  accurately 
pressed  into  the  groove  prepared  for  it,  and  the  wax  being  placed 
upon  the  inside  to  support  the  teeth  in  the  proper  position, 
body  is  filled  in  around  the  base  of  the  new^  ones,  which  are 
carved,  trimmed,  and  brushed,  so  as  to  save  the  crowns  of  the 
teeth  clean  and  properly  defined.  The  wax  is  then  carefully 
removed  from  the  piece,  and  more  body  is  filled  in  around  the 
teeth  upon  the  inside, — filling  up  the  grooves  over  the  pins,  and 
then  carving,  trimming,  etc.,  as  before,  to  give  it  the  desired 
form.  This  done,  if  the  teeth  are  set  a  little  apart,  and  it  is 
desired  to  keep  them  in  that  position,  take  a  small  piece  of 
asbestos  and  gently  press  it  in  between  the  teeth  at  the  cutting 
edges;  this  will  prevent  them  from  being  drawn  together  when 
the  body  is  being  baked.  The  piece  is  now  ready  for  the  fur- 
nace, but  it  should  not  be  baked  hard  enough  to  gloss  the  newly- 
applied  body  ;  it  should  have  more  the  appearance  of  Parian 
marble. 

This  being  done,  it  is  then  withdrawn  from  the  furnace  and 
transferred  to  a  cooling  muffle,  as  before  described.  When  suf- 
ficiently cool,  the  gum  enamel  is  applied  and  baked  with  a  sharp 
heat  until  it  becomes  smooth  and  glossy.  To  prevent  the  old 
gum  from  bleaching  or  becoming  lighter  colored  in  consequence 


DENTURES    WITH    CONTINUOUS    PORCELAIN    GUM.  487 

of  repeated  bakings,  a  very  thin  coating  of  fresh  gum  enamel 
should  be  lightly  brushed  over  the  entire  enameled  surface  of 
the  piece.  The  enamel  thus  applied  should  be  mixed  with  water, 
quite  thin,  so  as  to  flow  evenly  over  the  surface  when  applied 
with  a  camel's-hair  brush.  This  should  be  done  before  the  last 
baking,  that  the  whole  may  be  fused  at  the  same  time.  Ex- 
perience and  judgment  are  essential  requisites  in  order  to  pro- 
duce good  practical  results.  For  example,  if  the  carving  of  the 
body  is  not  properly  done,  the  form  and  shading  of  the  gum  and 
roof  will  not  appear  natural  when  the  work  is  finished  ;  if  the 
gum  enamel  is  put  on  too  thick,  it  will  produce  a  dark-red  color  ; 
if  not  thick  enough,  it  will  be  too  light ;  if  fused  too  hard,  it 
will  be  liable  to  craze  or  crack  ;  if  not  hard  enough,  it  will  be 
rough  or  granular ;  if  the  piece  becomes  gassed  in  baking,  it 
will  be  porous  and  of  a  bluish  color. 

General  Remarks. — The  teeth  of  different  persons  vary  as 
much  as  any  feature  of  the  face,  and  present  as  great  a  variety  of 
expressions.  Therefore,  in  the  construction  of  artificial  den- 
tures, the  dentist  should  select  and  arrange  the  teeth  with  special 
reference  to  each  individual  case.  The  length,  size,  form,  shade, 
and  position  of  the  teeth  should  be  varied  to  meet  all  the  dif- 
ferent physiognomical  requirements  that  occur  in  dental  practice. 

This  system  also  combines  with  great  advantage  the  restora- 
tion of  the  face  in  cases  where  the  muscles  have  become  sunken 
or  fallen  in  from  loss  of  the  teeth  and  consequent  absorption 
of  the  alveolar  processes.  .Here,  again,  the  artistic  skill  of  the 
dentist  is  brought  into  requisition.  He  should  study  the  face  of 
his  patient  as  the  artist  studies  his  picture,  for  he  displays  his 
genius  not  upon  canvas  but  upon  the  living  features  of  the  face  ; 
and  of  how  much  more  importance  is  the  living  picture,  that  reflects 
even  the  emotions  of  the  heart,  than  the  lifeless  form  upon  can- 
vas !  He  should  know  the  origin  and  insertion  of  every 
muscle  of  which  the  face  is  formed,  and  what  ones  he  is  to  raise, 
otherwise  he  will  be  liable  to  produce  distortion  instead  of 
restoration.  This  improvement  consists  of  prominences  made 
upon  the  denture  of  such  form  and  size  as  to  bring  out  each 
muscle  or  sunken  portion  of  the  face  to  its  original  fullness ;  and 
when  these  are  rightly   formed   they  are   not   detected  by  the 


488  MECHANICAL    DENTISTRY. 

closest  observer.  There  are  four  points  of  the  face  (of  many 
persons)  which  the  mere  insertion  of  the  teeth  does  not  restore, 
viz.,  one  upon  each  side  beneath  the  malar  or  cheek  bone,  and 
also  a  point  upon  each  side  of  the  base  of  the  nose,  in  a  line 
toward  the  front  portion  of  the  malar  bone. 

The  extent  of  this  falling-in  varies  in  different  persons, 
according  to  their  temperaments.  If  the  lymphatic  tempera- 
ment predominates,  the  change  will  be  slight.  If  nervous  or 
sanguine,  it  may  be  very  great.  The  muscles  situated  upon  the 
sides  of  the  face,  and  which  rest  upon  the  molar  or  back  teeth, 
are  the  zygomaticus  major,  masseter,  and  buccinator.  The  loss 
of  the  above  teeth  causes  these  muscles  to  fall  in.  The  principal 
muscles  which  form  the  front  portion  of  the  face  and  lips  are  the 
zygomaticus  minor,  levator  labii  superioris  alaeque  nasi,  and 
orbicularis  oris. 

These  rest  upon  the  incisor,  cuspid,  and  bicuspid  teeth, 
which,  when  lost,  allow  the  muscles  to  sink  in,  thereby  chang- 
ing the  form  and  expression  of  the  mouth. 

The  insertion  of  the  front  teeth  will,  in  a  great  measure, 
bring  out  the  lips,  but  there  are  two  muscles  in  the  front  portion 
of  the  face  which  cannot,  in  many  cases,  be  thus  restored  to 
their  original  position  ;  one  is  the  zygomaticus  minor,  which 
arises  from  the  front  part  of  the  malar  bone,  and  is  inserted  into 
the  upper  lip  above  the  angle  of  the  mouth ;  the  other  is  the 
levator  muscle,  which  arises  from  the  nasal  process  and  from 
the  edge  of  the  orbit  above  the  infraorbital  foramen.  It  is 
inserted  into  the  ala  nasi,  or  wing  of  the  nose  and  upper  lip. 

The  prominences  before  mentioned,  applied  to  these  four 
points  of  the  face,  beneath  the  muscles  just  described,  bring  out 
that  narrowness  and  sunken  expression  about  the  upper  lip  and 
cheeks  to  the  same  breadth  and  fullness  which  they  formerly  dis- 
played. If  skill  and  judgment  have  presided  over  all  parts  of 
the  operation,  the  result  will  be  highly  pleasing  and  of  practical 
utility.* 

*  Inasmuch  as  the  improvement  for  restoring  the  face  has  been  claimed  by  others, 
the  reader  is  referred  for  the  evidences  estabhshing  the  claim  of  Dr.  Allen  to  priority 
of  invention  to  the  historical  record  which  appears  in  the  old  American  Journal  of 
Dental  Science  of  1845.     In  the  published  proceedings  of  the  American  Society  of 


DENTURES    WITH    CONTINUOUS    PORCELAIN    GUM.  489 

Dr.  Hunter's  Formulas  and  Modes  of  Practice. — The  fol- 
lowing methods  of  compounding  and  applying  the  gum  materials, 
as  practiced  by  Dr.  W.  M.  Hunter,  were  taken  from  his  latest 
published  descriptions,  and  have  formed  the  basis,  in  a  large 
measure,  of  more  modern  methods  of  compounding  the  silicious 
materials  used  in  the  manufacture  of  body  and  gum  enamels. 

The  following  is  a  description  of  the  materials  and  compounds 
employed  : — 

"  Silcx  should  be  of  the  finest  and  clearest  description,  and 
kept  on  hand  ready  ground,  the  finer  the  better. 

"  Fused  spar  should  be  the  clearest  felspar,  such  as  is  used  by 
tooth  manufacturers  for  enamels,  completely  fused  in  a  porcelain 
furnace,  and  ground  fine. 

"  Calcined  borax  is  prepared  by  driving  off  the  water  of  crys- 
tallization from  the  borax  of  commerce,  by  heating  in  a  covered 
iron  vessel  over  a  slow  fire,  and  it  is  better  to  use  immediately 
after  its  preparation,  as  it  attracts  moisture.  It  should  be  per- 
fectly clean  and  white,  and  free  from  lumps. 

"  Caustic  Potassa  Optinius. — Known  also  as  potassa  fusa. 

"  Asbestos. — Take  the  ordinary  clean  asbestos,  free  it  from  all 
fragments  of  talc  or  other  foreign  substances,  and  grind  fine,  tak- 
ing care  to  remove  any  hard  fragments  that  may  occur. 

"  Granulated  Body. — Take  any  hard  tooth  material  (I  use 
the  following  formula  :  spar  3  oz.,  silex  i  ]/>  oz.,  kaolin  yi  oz.) 
and  fuse  completely.  Any  very  hard  porcelain,  wedgewood 
ware,  or  fine  china  will  answer  the  same  purpose.  Break  and 
grind  so  that  it  will  pass  through  a  wire  sieve,  No.  50,  and  again 
sift  off  the  fine  particles  which  will  pass  through  No.  10  bolting- 
cloth.  It  is  then  in  grains  about  as  fine  as  the  finest  gun- 
powder. 

"Flux. — Upon  this  depends  the  whole  of  the  future  opera- 
tions, and  too  much  care  cannot  be  taken  in  its  preparation.  It 
is  composed  of  silex  8  oz.,  calcined  borax  4  oz.,  caustic  potassa 

Dental  Surgeons  of  that  year  it  will  be  seen  that  a  medal  was  awarded  to  one  of  its 
members,  inscribed, "  Awarded  to  Dr.  John  Allen,  for  his  invention  for  restoring  the 
contour  of  the  face,  August,  1845."  This,  in  connection  with  the  fact  that  no  other 
record  upon  this  subject  is  found  in  our  dental  literature,  fixes  the  date  of  this 
improvement. 


490  MECHANICAL    DENTISTRY. 

I  oz.  Grind  the  potassa  fine  in  a  wedgewood  mortar  ;  gradually 
add  the  other  materials  until  they  are  thoroughly  incorporated. 
Line  a  Hessian  crucible  (as  white  as  can  be  got)  with  pure  kao- 
lin, fill  with  the  mass,  and  lute  on  as  a  cover  a  piece  of  fire-clay 
slab  with  the  same.  Expose  to  a  clear,  strong  fire  in  a  furnace 
with  coke  fuel  for  about  half  an  hour,  or  until  it  is  fused  into  a 
transparent  glass,  which  should  be  clear  and  free  from  stain  of 
any  kind,  more  especially  when  it  is  used  for  gum  enamels. 
Break  this  down,  and  grind  until  fine  enough  to  pass  through  a 
bolting  cloth,  when  it  will  be  ready  for  use. 

"  Base. — Take  flux  i  oz.,  asbestos  2  oz.,  grind  together  very 
fine,  completely  intermixing.  Add  granulated  body  i  ^  oz., 
and  mix  with  a  spatula  to  prevent  grinding  the  granules  of  body 
any  finer. 

"Gum  Enamels. — No.  i.  Flux  i  oz.,  fused  spar  i  oz.,  Eng- 
lish rose  40  grains.  Grind  the  English  rose  extremely  fine  in  a 
wedgewood  mortar,  and  gradually  add  the  flux  and  then  the  fused 
spar,  grinding  until  the  ingredients  are  thoroughly  incorporated. 
Cut  down  a  large  Hessian  crucible  so  that  it  will  slide  into  the 
muffle  of  a  furnace,  line  with  silex  and  kaolin  each  one  part,  put 
in  the  material,  and  draw  the  heat  up  on  it  in  a  muffle  to  the 
point  of  vitt'if action,  not  fusion,  and  withdraw  from  the  muffle. 
The  result  will  be  a  red  cake  of  enamel,  which  will  easily  leave 
the  crucible,  which,  after  removing  any  adhering  kaolin,  is  to  be 
broken  down  and  ground  tolerably  fine.  It  may  now  be  tested, 
and  then  (if  of  too  strong  a  color)  tempered  by  the  addition  of 
covering.  This  is  the  gum  which  flows  at  the  lowest  heat,  and 
is  never  used  when  it  is  expected  to  solder. 

"  No.  2.  Flux  I  oz.,  fused  spar  2  oz  ,  English  rose  60  grains. 
Treat  the  same  as  No.  i.  This  is  a  gum  intermediate,  and  is  used 
upon  platina  plates. 

"  No.  3.  Flux  I  oz.,  fused  spar  3  oz.,  English  rose  80  grains. 
Treat  as  the  above.  This  gum  is  used  in  making  pieces  intended 
to  be  soldered  on,  either  in  full  arches  or  in  the  sections  known 
as  block-zvork.  It  is  not  necessary  to  grind  very  fine  in  preparing 
the  above  formulae  for  application. 

"  Covering. — What  is  termed  covering  is  the  same  as  the 
formula  for  gum  minus  the  English  rose,  and   is  made  without 


DENTURES    WITH    CONTINUOUS    PORCELAIN    GUM.  49 1 

any  coloring  whatever  when  it  is  used  for  tempering  the  above 
gums  which  are  too  highly  colored,  and  which  may  be  done  by 
adding,  according  to  circumstances,  from  one  part  of  covering 
to  two  of  gum,  to  three  of  covering  to  one  of  gum,  thus  procur- 
ing the  desired  shade.  When  it  is  to  be  used  for  covering  the 
base  prior  to  applyingthe  gum,  it  may  be  colored  with  titanium., 
using  from  two  to  five  grains  to  the  ounce. 

"  Investment. — Take  two  measures  of  white  quartz  sand,  mix 
with  one  measure  of  plaster-of-Paris,  mixing  with  just  enough 
water  to  make  the  mass  plastic,  and  apply  quickly.  The  slab  on 
which  the  piece  is  set  should  be  saturated  with  water,  to  keep 
the  material  from  setting  too  soon,  and  that  it  may  unite  with  it. 

"  Cement. — Wax  i  oz.,  rosin  2  oz.  The  proportions  of  this 
will  vary  according  to  the  weather ;  it  should  be  strong  enough 
to  hold  the  teeth  firmly,  and  yet  brittle  enough  to  chip  away 
freely  when  cold.  A  little  experience  v>'ill  enable  any  one  to 
prepare  it  properly. 

"  After  the  plates  are  perfectly  adapted  to  the  mouth,  place 
wax  upon  each,  which  trim  to  the  proper  outline  as  regards 
length  and  contour  of  countenance*  marking  the  proper  occlusion 
of  the  jaws  and  the  median  line.  These  waxen  outlines  are 
called  the  (/nt/^s,  and  are  carefully  removed  from  the  mouth,  and 
an  articulation  taken  by  which  to  arrange  the  teeth. 

"  When  the  absorption  is  considerable  and  the  plate,  in  conse- 
quence, is  rather  flat,  it  is  necessary  to  solder  a  band  or  rim 
along  the  line  where  the  upper  draft  meets  the  plate,  about  one- 
sixteenth  or  one-eighth  of  an  inch  wide,  and  fitting  up  against 
the  outline  of  the  draft.  When  the  ridge  is  still  prominent,  the 
block  will  not,  of  course,  be  brought  out  against  the  lip  so  much, 
and  a  wire  may  be  soldered  on  instead  of  the  wider  band.  I 
think  one  or  the  other  necessary,  as  it  gives  a  thick  edge  to  the 
block,  rendering  it  far  less  liable  to  crack  off  than  if  it  were 
reduced  to  a  sharp  angle;  it  also  allows  the  edge  of  the  plate  to 
be  bent  in  against  the  gum,  or  away  from  it,  as  circumstances 
may  require,  and  affords  in  many  cases  a  far  better  support  for 
the  plates  than  can  be  given  to  one  in  which  the  band  is  struck 
up,  or  the  edge  turned  over  with  pliers,  where  the  block  must 
extend  to  the  edge  of  the  plate.    Some  few  cases  do  occur  where 


492  MECHANICAL    DENTISTRY. 

the  band  may  be  struck  as  far  back  as  the  bicuspids  with  advan- 
tage, and  some  in  the  lower  jaw  where  it  is  necessary  to  solder 
on  the  band,  but  the  general  practice  is  not  so. 

"  The  upper  teeth  are  first  arranged  on  the  plate  antagonizing 
with  the  lower  draft,  supported  by  wax  or  cement,  or  both. 
Then  remove  the  lower  draft  and  arrange  the  lower  teeth  so 
that  the  coaptation  of  the  cutting  edges  of  the  teeth  shall  be 
perfect  as  desired.  The  patient  may  now  be  called  in  again,  and 
any  change  in  the  arrangement  made  to  gratify  his  or  her  taste 
or  whim.  Now  place  the  plates  with  the  teeth  thereon  on  their 
respective  casts,  oil  the  cast  below  the  plate,  and  apply  plaster-of- 
Paris  over  the  edge  and  face  of  the  teeth  and  down  on  the  cast, 
say  an  inch  below  the  edge  of  the  plate.  This  will  hold  them 
firmly  in  their  place  while  you  remove  the  wax  and  cement  from 
the  inside  and  fit  and  rivet  backs  to  the  teeth.  When  backed, 
cut  the  plaster  through  in  two  or  more  places,  and  remove. 
Clean  the  plate  by  heating.  Cut  the  plaster  so  that  while  it 
will  enable  you  to  give  each  tooth  its  proper  position,  you  can 
readily  remove  it  from  the  teeth  when  they  are  cemented  to  the 
plate.  Adjust  the  sections  of  plaster  and  the  teeth  in  their 
proper  positions.  The  plaster  may  be  held  by  a  piece  of  soft 
wire.  Cement  the  teeth  to  the  plate  and  strengthen  the  cement 
by  laying  slips  of  wood  half  an  inch  long  along  the  joints  and 
against  the  teeth.  (I  generally  use  the  matches  which  are  so 
plenty  about  the  laboratory.)  Remove  the  sections  of  plaster, 
being  careful  not  to  displace  any  of  the  teeth.  If  it  be  intended 
to  cover  the  strap  with  enamel,  you  should  solder  a  wire  after 
backing,  and  previous  to  replacing  the  teeth,  along  the  plate 
parallel  with  the  bottom  of  the  straps,  and  about  one-eighth  or 
one-fourth  of  an  inch  from  them. 

"  The  teeth  are  now  backed  and  cemented  to  the  plate,  and 
present  an  open  space  between  the  plate  and  the  teeth,  which  is 
to  be  filled  up  with  the  base,  using  it  quite  wet  to  fill  up  the 
small  interstices,  filling  in  the  rest  as  hard  and  dry  as  possible. 
Fill  the  cavity  betivcen  the  plates  in  the  same  mafiner,  and  oil  the 
edge.  Oil  the  surface  of  the  base,  envelop  in  the  investment 
(precisely  as  you  would  put  an  ordinary  piece  into  plaster  and 
sand  for  soldering),  and  set  on  a  fire-clay  slab  previously  saturated 


DENTURES    WITH    CONTINUOUS    PORCELAIN    GUM.  493 

with  water.  When  hard,  chip  away  the  cement,  cooling  if  neces- 
sary with  ice,  until  it  is  perfectly  clean.  Along  the  joints  place 
scraps  and  filings  of  platina  very  freely, and  coverall  the  surface 
you  wish  to  enamel  with  coarse  filings,  holding  them  to  their 
place  by  borax  ground  fine  with  water.  Apply  pure  gold  as  a 
solder  quite  freely,  say  two  dwt.  or  more  to  a  single  set.  Put  in 
a  muffle  and  bring  up  a  gradual  heat  until  the  gold  flows  freely, 
which  heat  is  all  that  will  be  needed  for  the  base;  withdraw  and 
cool  in  a  muffle.  Remove  the  investment  and  fill  up  all  crevices 
and  interstices  not  already  filled,  with  covering  No.  2  ;  cover  the 
straps  and  base  with  the  same,  about  as  thick  as  a  dime,  and 
cover  this  with  gum  No.  2  about  half  that  thickness.  At  the 
same  time  enamel  the  base  in  the  chamber  and  cover  with  thick, 
soft  paper.  Set  the  plate  down  on  the  investment  on  a  slab,  with 
the  edges  of  the  teeth  up.  Fuse  in  a  muffle,  and  the  work  is 
completed.  Blemishes  may  occur  in  the  gum  from  a  want  of 
skill  in  the  manipulation;  should  such  occur,  remedy  by  apply- 
ing gum  No.  I. 

"Should  the  patient  object  to  the  use  of  platina  as  a  base, 
the  work  can  be  made  as  above  on  an  alloy  of  gold  and  platina 
20  carats  fine,  and  soldered  with  pure  gold,  etc.,  as  above.  In 
all  cases,  however,  where  it  is  used,  the  upper  plate  should  be 
made  as  I  have  described  above,  but  with  platina  any  kind  of 
plate  can  be  used. 

'•  Ordinary  Alloy. — Blocks  may  be  made  and  soldered  to  the 
ordinary  plate  if  the  absorption  is  sufficient  to  require  much 
gum,  without  any  platina.  Arrange  the  teeth  on  wax  on  the 
plate,  fill  out  the  desired  outline  of  gum,  and  apply  plaster  one- 
fourth  of  an  inch  thick  over  the  face  of  the  teeth,  wax,  and  cast. 
When  hard,  cut  it  into  sections  (cutting  between  the  canines 
and  bicuspids),  remove  the  wax  from  the  plate  and  teeth,  bind 
the  sections  of  the  plaster  mold  thus  made  to  their  places  with 
a  wire,  oil  its  surface  and  that  of  the  plate,  fill  in  the  space 
beneath  the  teeth  with  the  base,  wet  at  first,  but  toward  the  last 
as  hard  and  dry  as  possible,  and  thoroughly  compacted.  Trim 
to  the  desired  outline  on  the  inside,  oil  the  base,  and  fill  the 
whole  palatal  space  with  investment,  supporting  the  block  on  its 
lingual  side.     Remove  the  plaster  mold,  and  cut  through  the 


494  MECHANICAL    DENTISTRY. 

block  with  a  very  thin  blade  between  the  canines  and  the  bicus- 
pids. Take  the  whole  job  off  the  plate,  and  set  on  a  fire-clay- 
slab  with  investment,  the  edges  of  the  teeth  down  ;  bring  up  the 
heat  in  a  muffle  to  the  melting  point  of  pure  gold.  When  cold, 
cover  and  gum  with  No.  3  gum  and  covering. 

"Another  mode  is  to  back  the  sections  with  a  continuous  strap 
(using  only  the  lower  pin),  fill  in  the  base  from  the  front,  use 
covering  and  gum  No.  3,  finish  at  one  heat.  When  the  blocks 
are  placed  upon  the  plate,  the  other  pin  is  used  to  fasten  the  gold 
back,  which  is  soldered  to  it  and  the  platina  half-back  ;  neither 
of  these  backs  need  be  very  heavy,  as  soldering  the  two  together 
gives  great  strength  and  stiffness.  Very  delicate  block-work 
can  be  made  in  this  way,  and  it  is  applicable  also  where  a  few 
teeth  only  are  needed. 

"A  very  pretty  method,  where  a  section  of  two  or  four  teeth 
(incisors)  is  needed,  and  only  a  thin  flange  of  gum,  is  to  fit  gum 
teeth  into  the  space,  unite  by  the  lower  platina  with  the  con- 
tinuous back,  and  unite  the  joint  with  gum  No.  3.  A  tooth  left 
ungummed  by  the  manufacturer  would  be  best  for  the  purpose. 
The  same  may  be  applied  to  blocks  for  a  full  arch,  remembering 
not  to  depend  entirely  upon  platina  backs. 

"  The  method  I  prefer  for  full  arches  on  ordinary  plate  is  to 
take  a  ribbon  of  platina,  a  little  wider  than  the  intended  base, 
and  of  the  length  of  the  arch,  cut  it  nearly  through  in  five 
places,  viz.,  between  the  front  incisors,  between  the  lateral  incisors 
and  canines,  and  between  the  bicuspids.  Adapt  it  to  the  form 
of  an  alveolar  ridge  with  a  hammer  and  pliers,  and  swage  on  the 
plate  along  where  the  teeth  are  to  be  set.  Solder  up  the  joints 
with  pure  gold,  and  proceed  to  back  the  teeth,  etc.,  as  before  ; 
making  preparations  for  fastening,  and  removing  the  slip  of 
platina  from  the  gold  plate  before  enveloping  in  the  investment, 
when  proceed  as  before. 

"  When  the  teeth  are'  arranged,  insert  four  platina  tubes,  about 
one  line  in  diameter,  two  between  the  molars,  and  two  between 
the  cuspids  and  bicuspids,  and  solder  to  the  platina  base.  These 
are  designed,  after  the  teeth  are  finished,  to  be  the  means  of 
fastening  to  the  gold  plate,  either  by  riveting  in  the  usual  way, 
or  by  soldering  pins  to  the  gold  plate  passing  up  through  the 


DENTURES    WITH    CONTINUOUS    PORCELAIN    GUM.  495 

tubes,  fastening  with  sulphur  or  wooden  dowels.  By  these 
methods  we  are  enabled  to  readily  remove  the  block  and  repair 
it,  should  it  meet  with  any  accident,  and  also,  in  case  absorption 
should  go  on,  to  restrike  the  plate  or  to  lengthen  the  teeth. 
The  rim  should  be  put  on  the  gold  plate  after  the  block  is 
finished  ;  it  gives  additional  strength  and  a  beautiful  finish. 

"  Memoranda. — In  preparing  material  always  grind  dry,  and 
the  most  scrupulous  cleanliness  should  attend  all  of  the  manipu- 
lations. In  all  cases  where  heat  is  applied  to  an  article  in  this 
system,  it  should  be  raised  gradually  from  the  bottom  of  the 
muffle  and  never  run  into  a  heat.  Where  it  is  desired  to  lengthen 
any  of  the  teeth,  either  incisors  or  masticators,  or  to  mend  a 
broken  tooth,  it  may  be  done  with  covcn)ig,  properly  colored 
with  platina,  cobalt  or  titanium. 

"  In  preparing  a  piece  of  work,  wash  it  with  great  care,  using 
a  stiff  brush  and  pulverized  pumice-stone.  Bake  over  a  slow 
fire  to  expel  all  moisture,  and  wash  again,  when  it  will  be  ready 
for  any  new  application  of  the  enamel.  Absorption,  occurring 
after  a  case  has  been  worn  some  time,  by  allowing  the  jaws  to 
close  nearer,  causes  the  lower  jaw  to  come  forward  and  drive 
the  upper  set  out  of  the  mouth.  By  putting  the  covering  on  the 
grinding  surface  of  the  back  teeth  in  sufficient  quantities  to 
make  up  the  desired  length,  the  coaptation  of  the  denture  will 
be  restored,  and  with  it  the  original  usefulness. 

"  Any  alloy  containing  copper  or  silver  should  not  be  used 
for  solder  or  plate,  if  it  is  intended  to  fuse  a  gum  over  the 
lingual  side  of  the  teeth,  as  it  will  surely  stain  the  gum.  Simple 
platina  backs  alone  do  not  possess  the  requisite  stiffness,  and 
should  always  be  covered  on  platina  with  the  enamel,  and  on 
gold  with  another  gold  back.  In  backing  the  teeth,  lap  the 
backs  or  neatly  join  them  up  as  far  as  the  lower  pin  in  the 
tooth,  and  higher  if  admissible,  and  in  soldering  be  sure  to 
have  the  joint  so  made  perfectly  soldered'' 

Dr.  Haskell's  Methods. — "  It  should  be  borne  in  mind  that 
the  strength  of  this  work  depends  mainly  upon  the  metal,  and 
not  upon  the  porcelain,  though  the  latter  adds  to  its  strength. 
While  platinum  is  a  very  soft  metal,  yet,  by  means  of  various 
devices,    the    plate,    with   the  teeth  properly  soldered   on,    and 


496  MECHANICAL    DENTISTRY. 

ready  for  the  porcelain,  can  be  made  very  stiff  and  strong, 
therefore  everything  that  can  be  done  to  secure  a  strong  founda- 
tion should  be  carefully  observed. 

"  The  plate  should  be  of  the  best  French  material  (not  melted 
scraps  and  old  plates),  29  to  30  gauge  for  the  upper,  and  26  to 
28  for  the  lower,  and  should  be  swaged  on  Babbitt  metal  dies. 
The  plate  is  then  tried  in  the  mouth,  and  if  the  fit  is  found  to  be 
correct,  arrange  the  articulating  wax,  secure  the  '  bite,'  and 
make  the  articulating  model. 

"  The  back  of  the  plate  should  be  doubled,  for  the  following 
reasons  :  It  imparts  increased  strength  ;  leaves  some  margin 
for  change,  in  case  of  necessity,  after  the  work  is  in  the  mouth  ; 
protects  the  edge  of  the  porcelain  ;  and  admits  of  a  neater  finish. 
This  *  doubler  '  should  be  about  three-sixteenths  of  an  inch 
wide,  with  the  edge  turned  up  slightly  to  receive  the  porcelain. 
Around  the  outer  edge,  solder  a  flattened  wire,  one-sixteenth  of 
an  inch  wide,  or  less,  and  22  gauge,  bringing  the  ends  to  meet 
the  turned  edge  of  the  doubler.  This  strengthens  the  plate, 
and  affords  a  good  round  finish  to  the  edge,  as  well  as  protec- 
tion to  the  porcelain.  This  is  easily  put  on  after  a  little 
practice,  and  is  far  preferable  to  turning  the  edge  of  the  plate 
with  pliers,  or  otherwise.  Pure  gold  should  always  be  used  for 
soldering,  and  with  just  enough  bora.x  (using  very  little)  to  give 
direction  to  the  flow  of  solder. 

"  Then  comes  the  arrangement  of  the  teeth,  and  this  should 
always  be  done  in  the  mouth,  the  articulating  model  being  only 
a  preliminary  guide ;  for  by  the  mouth  alone  can  one  determine 
the  correct  expression  and  arrangement  desired  ;  and  it  is  just 
here  that  three-fourths  or  more  of  the  artificial  dentures  fail  in 
an  utter  lack  of  artistic  skill.  In  this  work  there  is  ample 
opportunity  for  the  display  of  taste  and  skill,  so  that  perfection 
itself  is  attained  at  the  hands  of  the  true  artist. 

"  The  investing  process  comes  next.  First,  a  coat  of  shellac 
over  the  teeth  to  prevent  etching  (although,  if  this  occurs,  it  is 
not  a  matter  of  much  account,  as  the  baking  remedies  it). 
Then  a  tJiin  coat  of  clear  plaster  ;  next  plaster  and  asbestos,  one 
part  of  the  latter  to  two  of  the  former.  Let  the  portion  under 
the   plate  extend   at  least  one  inch  back  of  the  latter,  as  this 


DENTURES    WITH    CONTINUOUS    PORCELAIN    GUM.  497 

bottom  portion  is  to  be  retained  on  which  to  bake  the  case ;  invest 
the  whole  one-half  inch  thick.  Warm  the  case  until  the  plate 
is  sufficiently  heated  to  remove  the  wax  easily ;  dash  boiling 
water  over  it  (this  is  the  best  method  to  remove  wax  adhering 
to  teeth  and  plate  in  all  kinds  of  work).  The  backings  should 
be  co7itimious  and  be  lapped  on  to  the  plate,  for  in  this  is  the 
mainstay  of  the  work  for  strength.  Cut  patterns  in  tin  or  lead, 
three  pieces,  one  for  the  six  front  teeth  and  one  for  each  side, 
lapping  over  the  cuspid  teeth  ;  the  foot-piece  should  lap  on  to  the 
plate  about  three-sixteenths  of  an  inch.  No  borax  is  needed. 
The  gold  should  be  melted  and  rolled  into  a  ribbon  as  thin  as 
possible,  and  cut  in  small  pieces  and  laid  under  the  lap,  or  foot- 
piece,  and  a  piece  under  each  pin.  The  backings  can  be  fitted 
more  easily  by  splitting  the  foot-piece.  The  most  convenient 
method  of  soldering  is  in  the  furnace,  being  careful  not  to  let  it 
remain  too  long,  so  as  to  fuse  the  enamel  on  the  teeth.  If  a  pin 
should  fail  to  solder,  it  is  immaterial,  as  the  '  body'  will  hold  it. 

"  After  cooling,  remove  the  plaster  and  save  the  base.  If  any 
teeth  are  etched,  sandpaper  them  and  remove  every  particle  of 
plaster;  with  a  sharp  instrument  scarify  the  surface  of  the  plate. 
Place  the  plate  on  the  articulating  model,  and  if  it  is  sprung, 
press  it  into  place,  which  is  very  readily  done. 

"  The  '  body,'  and  enamel  or  gum  color,  as  prepared  by  S.  L. 
Close,  is  the  only  reliable  material  to  be  had,  as  Dr.  Allen  no 
longer  furnishes  it  for  the  trade.  Apply  the  '  body '  mixed  with 
water,  quite  thin,  by  means  of  an  oval-pointed  knife,  occasion- 
ally jarring  with  handle  of  spatula,  and  as  the  moisture  comes  to 
the  surface,  absorb  with  a  cloth  ;  after  it  is  well-filled  into  all 
interstices,  apply  it  thicker,  jarring,  absorbing,  and  packing  hard, 
until  enough  is  on  the  outside  to  produce  the  proper  shape  and 
contour  of  the  lips.  Then  apply,  with  the  curved  point  of  the 
knife,  the  body  to  the  lingual  side  of  the  plate,  same  as  on  the 
outside,  but  only  a  thin  coat  on  the  plate.  Trim  around  the 
necks  of  the  teeth,  remove  all  particles  from  bctiveen  with  a  quill 
toothpick,  and  brush  ail  particles  off  the  surface  of  the  teeth  and 
exposed  portions  of  plate,  and  the  case  is  ready  for  baking. 

"  The  Philadelphia  furnace,  sold  by  all  dealers  in  dental  goods, 
we  prefer.  It  is  always  best  to  use  the  largest  size,  No.  i,  yet 
.^2 


498  MECHANICAL    DENTISTRY. 

No.  2  will  do  if  the  larger  size  cannot  be  had.  Be  sure  of  a 
good  draft.  The  furnace  can  be  used  as  it  comes;  a  better 
plan  is  to  knock  the  bottom  out  of  the  lower  section,  get  longer 
bars,  that  will  extend  some  distance  through  the  front,  the  two 
center  ones  at  least  eighteen  inches.  Build  a  hearth,  two  bricks 
thick  and  three  feet  square;  build  an  enclosure  of  brick,  about 
twelve  inches  high,  large  enough  to  set  the  furnace  on,  and  line 
with  fire-brick.  Provide  a  sheet-iron  cover  for  the  front,  to 
close  the  draft. 

"  In  setting  the  '  muffle,'  see  that  the  vent  hole  in  the  top  is 
clear ;  this  is  for  escape  of  gas  that  may  be  in  the  muffle  and 
would  injure  the  work.  Fasten  the  front  end  with  fire-clay,  but 
leave  the  back  end  free. 

"  The  fuel  to  be  used  must  be  anthracite  coal  or  else  coke ; 
Lehicrh,  range  size,  is  the  best. 

"  A  sheet-iron  shelf,  the  edge  bent  into  the  space  between  the 
furnace  and  cover,  and  with  a  leg  riveted  to  it  and  resting  on  the 
long  bars,  is  needed  to  set  the  case  on,  to  heat  up,  and  run  into 
the  muffle  gradually.  Set  the  case  ten  or  twelve  inches  from  the 
opening,  move  forward,  every  ten  or  fifteen  minutes,  a  couple  of 
inches,  until  it  is  in  the  muffle  ;  place  it  within  two  inches  of 
the  back,  and  close  the  door.  If  the  heat  is  right,  five  or  ten 
minutes  will  suffice  ;  still,  it  must  be  looked  at  so  as  not  to  get 
too  much  heat.  This  first  bake  should  be  only  a  glaze.  Remove 
to  a  muffle  on  the  hearth  and  close  up  tight.  When  cool,  place 
on  the  model,  and,  if  sprung,  press  it  into  place.  Next  fill  up  all 
the  cracks  with  very  thin  body,  jarring  with  handle  of  the  spatula 
often,  so  that  the  material  will  fill  up  thoroughly  ;  then  spread 
on  thicker  until  the  proper  shape  and  fullness  are  secured,  trim- 
ming around  the  teeth,  and  doing  as  previously  described,  and 
bake  as  before.  After  cooling,  the  enamel  is  to  be  put  on  the 
same  as  the  body,  applying  only  a  thin  and  uniform  coat.  The 
rugae  can  be  produced  in  the  body  or  in  the  gum.  The  enamel 
should  have  a  thoroughly  glossy  appearance  when  ready  to 
be  removed  from  the  furnace.  Heated  cooling  muffles  are 
unnecessary,  as  the  case  itself  will  heat  the  muffle  all  that  is 
necessary. 

"  Lower  sets  are  better  without  a  binding,  as  it  is  sometimes. 


DENTURES    WITH    CONTINUOUS    PORCELAIN    GUM.  499 

necessary  to  file  or  grind  away  the  edge.     Use  plate  No.  8,  or 
even  thicker,  and  solder  on  the  edge  a  narrow  strip, yf«/. 

"  The  case  is  finished  by  filing  and  polishing  the  exposed 
metal  surface,  not  doing  anything  to  the  upper  surface. 

"  A  '  defined  '  air-chamber  is  rarely  necessary, — a  Cleveland 
chamber,  never.  Raise  the  plate  over  the  hard  palate  with  a 
thin  film  of  wax  on  the  plaster  cast,  chamfering  off  the  edges 
completely ;  scrape  the  plaster  model  across  the  back,  except 
right  in  the  center,  according  to  the  softness  of  the  palate. 

"  This  work  is  not  advisable  for  partial  sets,  except  in  some 
partial  lower  cases  where  there  are  no  detached  teeth.  In  these 
cases,  the  plate  should  be  at  least  two  thicknesses  across  the  back 
of  the  front  teeth,  and  resting  well  up  on  the  necks  of  the  same. 

"  Very  few  seem  to  know  how  to  prepare  a  case  for  repairing. 
Invest  it  in  plaster  and  asbestos  at  least  one-half  of  an  inch 
deep ;  place  in  the  muffle  before  lighting  the  fire,  and  allow 
it  to  remain  with  the  door  open,  as  the  fire  comes  up,  until  it  is 
red  Jiot ;  then  remove,  cool,  and  thoroughly  clean  off  the  plaster, 
preserving  the  base,  and  it  can  be  run  into  the  furnace  with  as 
little  danger  of  cracking  as  if  it  had  never  been  worn. 

"  Grind  out  the  remains  of  the  teeth  below  the  margins  of 
the  gum  ;  select  a  rubber  tooth,  as  it  is  easier  to  get  and  just  as 
good  as  one  made  for  this  work,  filing  off  the  pins  ;  hold  with 
wax  until  a  little  plaster  and  asbestos  can  be  placed  over  it  and 
the  adjoining  teeth  ;  thoroughly  remove  the  wax  and  put  on 
repairing  body,  and  bake;  cool,  put  on  the  gum,  having  pre- 
viously ground  off  a  portion  of  the  old  gum  if  it  is  a  very  old 
case,  and  put  on  just  a  little  new,  and  bake  as  at  first. 

"  If  blisters  occur,  grind  into  them  and  fill  with  body  and giini, 
three  to  one,  press  hard,  and  enamel." 

Dr.  Field's  Methods. — "  When  the  platinum  has  once  touched 
the  metal  dies,  never  place  it -under  the  blowpipe  without  its  hav- 
ing been  thorougldy  pickled.  This  is  often  neglected,  and  the 
consequence  is  that  the  plate  will  become  more  or  less  discol- 
ored from  the  absorption,  under  heat,  of  the  baser  metal  into  the 
platinum.  When  the  teeth  are  properly  arranged  with  wax  on 
the  plate,  as  directed  by  Dr.  Allen,  invest,  but  use  no  sand,  simply 
plaster  and  asbestos.     My  reason  for  this  I  will  give  further  on. 


500  MECHANICAL    DENTISTRY. 

"  After  the  investment  has  become  sufficiently  hard  to  handle, 
the  backings  may  be  adjusted  ;  and  here  I  shall  differ  somewhat 
with  Dr.  Allen,  for,  instead  of  the  contiimous  backing,  I  back 
each  tooth  separately,  and  for  two  reasons,  one  of  which  is,  that 
I  think  my  work  will  be  stronger  when  completed,  by  allowing 
the  body  to  be  well  w^orked  in  between,  below,  and  completely 
around  the  teeth  without  a  platinum  wall,  as  it  were,  separating 
the  body  on  a  line  running  completely  around  the  alv^eolar  ridge, 
and  only  just  touching  over  the  top  of  this  platinum. 

"  My  second  reason  is  that,  should  the  teeth  be  drawn  out  of 
place  any,  as  is  sometimes  the  case  by  the  cracking  of  the  invest- 
ment and  pulling  away  from  the  plate,  the  single  backing  of  each 
tooth  admits  of  a  much  easier  and  more  perfect  readjustment  than 
when  the  backing  is  continuous.  Make  the  backings  of  a  some- 
what V  shape,  that  is,  let  them  be  a  little  narrower  at  the  top 
than  where  they  come  in  contact  with  the  plate  ;  bend  up  the 
lower  part  of  the  backing  to  the  extent  of  about  one-sixteenth 
of  an  inch,  and  at  such  an  angle  that  when  placed  in  position 
behind  the  platinum  pin,  to  which  it  is  to  be  soldered,  it  will  fit 
fairly  and  squarely  on  the  plate  ;  put  in  position  and  press  the 
pin  down  on  it,  first  having  placed  a  piece  of,  say  number  20, 
gold  foil,  folded  two  or  three  times,  one-sixteenth  of  an  inch 
square,  against  the  backing,  so  that  when  the  pin  is  bent  down 
upon  it,  it  will  hold  it  from  slipping  away  ;  then  with  a  pair  of 
ordinary  plugging  pliers  squeeze  the  foil  up  to  and  around  the 
pin  ;  then  place  one  or  two  pieces  of  solder  (pure  gold)  just 
behind,  and  close  against,  the  heel  of  the  foot-shaped  backing. 
By  placing  it  here,  the  danger  of  it  slipping  away  when  the 
borax  calcines  under  heat  is  avoided.  The  less  solder  you  use, 
and  still  have  your  teeth  fastened,  the  better,  for  the  reason  that 
the  gold  flowing  at  a  less  heat  than  that  required  for  the  fusing 
of  the  body,  the  gold  is  in  a  slate  of  fusion  ivhen  the  body  has  set, 
and  there  will  be  no  adhesion  between  the  gold  and  the  body. 
Now  solder  as  most  convenient.  I  find  the  Fletcher  furnace  an 
admirable  contrivance  for  this  purpose,  ten  minutes  being  all 
the  time  necessary  to  complete  the  work.  Remove  the  investment 
carefully,  and  preserve  it  all  for  future  use.     The  plate  is  then 


DENTURES    WITH    CONTINUOUS    PORCELAIN    GUM.  50I 

tried  in  the  mouth,  and  the  teeth  nicely  adjusted  to  those  with 
which  they  are  to  antagonize. 

"  Everything  is  now  ready  for  the  first  baking.  Pour  out 
upon  a  clean  butter  plate  the  amount  of  body  required,  into 
which  pour  sufficient  pure  water  to  make  a  tJiiii  paste,  and  then 
begin  the  work  of  molding  and  carvang  the  piece  by  filling  in 
between  and  under  all  the  teeth,  tapping  your  plate  gently  from 
time  to  time;  this  will  bring  the  water  to  the  surface  and  settle 
the  body  into  every  nook  and  crevice.  After  each  tapping  ab- 
sorb the  surface  water  with  a  clean  napkin  ;  by  so  doing,  you 
will  the  better  hold  the  body  to  its  place  and  prevent  its  running 
where  not  wanted.  Build  over  the  roots  of  the  incisors  and 
cuspids  boldly,  leaving  a  corresponding  depression  between  the 
teeth  ;  thus  when  the  piece  is  completed,  you  will  have  that 
natural  and  life-like  appearance  as  of  the  roots  of  the  teeth 
showing  slightly  through  the  gum. 

"  Now  take  that  part  of  your  investing  material  that  covered 
the  teeth  when  the  piece  was  soldered,  grind  it  up  fine,  and 
with  it  make  a  cushion  an  inch  thick,  on  the  slab  that  is  to 
hold  the  case  ;  then  place  your  piece  on  this  base,  teeth  doivn- 
zuard,  take  a  small  spatula  and  work  the  powdered  material  well 
up  against  the  teeth,  so  that  the  bearing  shall  be  equal  under 
every  tooth ;  this,  if  properly  done,  will  prevent  any  drazving 
away  of  the  teeth  from  their  proper  position,  as  is  frequently  the 
case  when  the  plate  is  placed  in  the  muffle  with  the  teeth  upward, 
the  cause  being  the  shrinkage  of  the  body ;  and  now  comes  my 
reason  for  not  using  sand  in  this  investing  material,  viz.,  the  sand, 
acting  as  a  flux,  would  attach  itself  more  or  less  to  the  teeth 
themselves,  and  I  have  seen  this  thing  carried  so  far,  when  the 
heat  was  a  little  too  high,  as  to  solidly  fuse  teeth  and  slab 
together. 

"  The  piece  is  now  ready  for  the  first  baking,  and  this  should 
be  carried  no  farther  than  to  shrink  the  body  as  much  as  possi- 
ble, not  going  beyond  a  semi-fuse.  After  this  is  completed,  and 
the  case  cooled,  proceed  to  fill  up  all  cracks  and  shrinkage  by 
the  application  of  more  body,  when  the  case  is  ready  for  the 
second  baking.     This  should  be  done  with  the  plate  reversed, 


502  MECHANICAL    DENTISTRY. 

teeth  upward,  using  for  a  support  that  part  of  the  investment 
which  came  in  contact  with  the  platinum,  and  which  should  be 
preserved  unbroken.  In  the  second  baking  of  the  body,  care 
should  be  taken  that  it  be  not  overdone.  A  piece  properly 
baked  will  present  a  beautifully  granulated  appearance,  the  tips 
of  the  granules  sparkling  like  little  dewdrops.  Carrying  the 
heat  beyond  the  stage  necessary  to  produce  this  effect  vitrifies 
the  body,  thereby  very  much  lessening  the  strength  of  the  work 
when  completed. 

"  If  now  it  is  found  that  a  third  body  is  not  required  (and  it 
rarely  is,  if  proper  care  has  been  taken  with  the  work  so  far, 
although  occasionally  it  may  be  necessary),  proceed  with  the 
enameling  as  directed  by  Dr.  Allen.  Should  there  be  any  little 
rough  spots  on  the  teeth,  caused  by  overheating  when  soldering, 
paint  them  over  with  a  little  clean  pulverized  borax  mixed  with 
water;  this  will  flow  the  tooth  enamel,  and  cause  them  to  come 
out  from  the  muffle  as  bright  and  smooth  as  when  they  first  left 
the  factory. 

"  The  work  is  now  ready  for  its  third  or  final  baking,  which 
should  be  with  a  quick,  sharp  fire.  When  fused,  draw  to  the 
front  part  of  the  muffle  ;  put  in  the  muffle  plug,  then  dump 
the  fire,  and  leave  until  the  furnace  is  cold ;  by  so  doing,  the 
case  is  well  annealed,  and  all  danger  of  checking  the  enamel 
avoided.  Twenty  or  thirty  minutes  now  are  all  that  are  neces- 
sary for  what  little  finishing  the  plate  will  require,  when  it  will 
be  ready  for  the  mouth. 

"  Let  it  be  remembered  by  the  beginner  that  on  the  carving  of 
the  first  body  largely  depends  the  artistic  beauty  of  the  work. 
Keep  your  patient's  face  well  before  you  in  your  mind's  eye,  and 
reproduce  in  porcelain  all  those  little  minor  details  which,  when 
properly  arranged  and  blended  together,  shall  so  counterfeit 
nature's  handiwork  that  that  of  man  can  hardly  be  detected." 

Dr,  Ambler  Tees's  Methods  and  Formulas. — "  Continuous- 
gum  work  is  mounted  upon  a  swaged  plate  of  pure  platina, 
about  No.  29,  American  gauge.  The  lower  plate,  to  insure 
strength,  is  made  of  two  pieces  soldered  together,  one  being 
large  enough  to  allow  for  a  rim.  In  a  partial  lower  set,  an 
additional  piece   of  iridionized   platina   is  soldered  to  the  part 


DENTURES    WITH    CONTINUOUS    PORCELAIN    GUM.  503 

covering  the  lingual  gums  of  the  remaining  natural  teeth. 
Plain  teeth,  with  single  long  pins,  made  for  the  purpose  by  tooth 
manufacturers,  are  soldered  to  the  plate  with  pure  gold  (24  k.), 
which  alone  is  used  as  a  solder  in  this  work,  since  the  copper 
and  silver  contained  in  alloyed  gold  will  discolor  'Oat.  gum  enamel. 
The  silicious  materials  called  body  and  giun  enamel  are  then 
applied  around  the  necks  of  the  teeth,  and  upon  the  lingual 
portion  of  the  plate,  by  means  of  small  spatulas,  and  carved  to 
imitate  the  contour  of  the  gum. 

"  The  investment  used  for  retaining  the  teeth  in  position  while 
being  soldered  is  composed  of  two  parts  of  plaster  and  one  of 
asbestos  ;  before  applying  this,  the  teeth  should  be  coated  with 
a  thick  varnish  of  shellac  and  alcohol,  to  prevent  the  teeth  being 
etched  in  soldering.  The  backing  is  fitted  most  conveniently  by 
making  it  of  three  pieces ;  the  pins  are  bent  down  over  it,  and 
soldered  with  pure  gold.  After  soldering,  the  investment  is 
removed,  and  the  teeth  and  the  plate  brushed  with  soap-suds 
and  powdered  pumice-stone  and  washed  off  with  clean  water. 
T\\&  first  coat  of  body  is  then  applied,  moistened  with  clean  water 
to  the  consistency  of  soft  putty,  as  a  foundation,  no  effort  being 
made  to  imitate  the^contour  of  the  gums  ;  separations,  however, 
are  made  between  the  teeth,  so  that  the  body  may  fuse  around 
each  tooth  separately,  and  prevent  it  being  drawn  from  position 
by  the  shrinkage  of  the  body.  It  is  then  fused  in  the  muffle, 
and  placed  in  a  cool  muffle  for  thirty  minutes.  After  adjusting 
it  upon  the  articulator,  it  is  ready  for  the  second  coat  of  body.  In 
applying  this,  an  artistic  effort  is  made  to  imitate  the  contour  of 
the  gums  ;  and  by  making  elevations  and  depressions  in  appro- 
priate position,  the  lights  and  shades  of  the  natural  gums  may 
be  simulated,  especial  attention  being  paid  to  the  rugae.  This 
coat  is  vitrified  and  not  fused.  After  it  is  cool  and  again 
adjusted  upon  the  articulator,  the  gum  enamel  is  applied,  the 
spatulas  being  used  for  the  purpose.  It  is  moistened  with 
clean  water,  a  little  thinner  than  the  body,  and  laid  on  a  little  at 
a  time,  about  the  thickness  of  twenty-six  plate.  This  is  fused 
and  allowed  to  remain  in  the  cool  muffle  for  an  hour  and  a  half. 
The  platina  is  then  rubbed  with  pumice-stone,  an  orange-wood 
stick  being  used,  and  the  rim  filed,  stoned,  and  burnished,  when 
the  set  will  be  ready  for  the  mouth. 


504  MECHANICAL    DENTISTRY. 

"  When  a  set  is  to  be  repaired,  tlie  mucus  should  be  burnt  off 
before  any  fresh  body  is  applied.  To  accomplish  this,  it  should 
be  invested  in  plaster  and  asbestos,  and  heated  to  redness  over  a 
gas  or  coal-oil  stove,  or  upon  the  coals  in  a  range.  The  invest- 
ment should  then  be  removed,  the  set  washed  with  soap-suds 
and  pumice-stone,  and  again  heated  to  redness  upon  a  slide 
in  the  muffle.  The  new  tooth,  after  being  carefully  ground 
against  the  gum,  is  held  in  position  by  plaster  and  asbestos  on 
the  palatine  surface,  a  very  small  quantity  being  sufficient;  after 
it  has  set,  giini  enamel  is  worked  into  the  joint  at  the  neck  and 
fused  in  the  muffle.  The  body  and  gum  enamel  are  then  applied 
to  the  palatine  surface,  after  the  pin  is  soldered  to  the  old  back- 
ing, and  then  fused.  This  plan  obviates  the  old  method  of 
investing  the  whole  set  in  plaster  and  asbestos. 

"  Dr.  Allen's  formulas  have  never  been  published.  For  many 
years  Dr.  S.  L.  Close,  of  New  York,  at  one  time  connected  with 
Dr.  Allen,  has  manufactured  the  materials  for  the  profession,  and 
these  can  be  relied  upon.  From  time  to  time,  however,  materials 
have  been  placed  upon  the  market  purporting  to  be  Allen's, 
which  have  checked  very  much  in  cooling." 

Body  and  gum  enamel  for  continuous-gum  work,  was  manu- 
factured by  the  late  Dr.  Tees,  according  to  the  following  formulas 
and  methods  of  compounding. 

He  furnished  three  shades  of  gum  enamel — pale,  medium,  and 
dark.     The  body  as  made  by  him  is  composed  of 

Felspar, 2  ozs. 

Dental  glass, 8  dwts. 

Kaolin, 3  dwts. 

The  materials  are  ground  together  in  a  moistened  state,  in  a 
wedgewood  mortar,  for  about  an  hour;  then  dried;  again 
ground  for  ten  minutes,  and  fused  in  a  crucible  in  a  coke  fire,  or 
upon  a  slide  in  the  muffle.  After  being  pulverized,  two  grains 
of  titanium  to  each  ounce  are  added  and  thoroughly  mixed. 

The  gum  enamel  is  composed  of 

Felspar, 2  ozs. 

Dental  glass, 10  dwts. 

Gum  frit, ;^  dwt. 

These  materials  are  ground  together  in  a  moistened  state,  for 


DENTURES    WITH    CONTrNUOUS    PORCELAIN    GUM.  505 

about  an  hour,  in  a  wedgewood  mortar  ;  then  dried,  ground  again 
for  ten  minutes,  and  fused- — upon  a  sUde  rubbed  with  fine,  dry 
silex — in  the  muffle  of  the  furnace;  again  pulverized,  and  suffi- 
cient additional  gum  frit  mixed  in  with  a  spatula  to  give  the 
desired  shade. 

The  materials  fuse  kindly  and  will  not  check  in  cooling. 

Application  of  Continuous  Gum  to  Partial  Sets. — The 
following  method  of  constructing  partial  sets  of  artificial  teeth 
with  continuous  gum  is  taken  from  a  practical  and  well-written 
paper  on  this  process  by  Dr.  W.  B.  Roberts  : — 

"  Partial  cases  maybe  made  of  continuous  gum  ;  but  the  work 
is  so  various  in  its  nature,  that  the  dentist  must  necessarily  de- 
pend much  upon  his  own  judgm.ent.  Difficult  cases  will  con- 
stantly present  themselves  that  will  require  the  exercise  of  much 
study  and  ingenuity,  in  which  the  general  instruction  that  can 
be  given  in  words  may  be  of  but  little  service.  The  first  attempt 
of  this  kind  in  my  own  experience  was  in  replacing  two  central 
incisors.  Taking  two  continuous-gum  teeth,  I  placed  upon  them 
a  platinum  lining,  sHtting  this  down  along  the  edge  of  one  tooth 
nearly  through  the  piece  and  up  the  edge  of  the  other  tooth  by 
a  parallel  cut,  leaving  the  two  parts  joined  together  by  a  narrow 
slip.  This  allowed  sufficient  motion  between  the  teeth,  so  that 
they  could  be  adjusted  as  desired.  I  then  placed  a  small  piece  of 
tissue  paper  on  the  plaster  model,  covering  the  spot  to  be  occu- 
pied by  the  teeth  and  gum,  to  prevent  the  adhesion  of  the  body 
to  the  plaster,  and  holding  the  two  incisors  in  their  places,  worked 
the  body  into  all  the  depressions  of  the  gum  and  around  the 
roots  of  the  teeth.  It  was  then  all  removed  from  the  model, 
and  placed  in  a  paste  of  pulverized  silex,  or  plaster  and 
asbestos,  upon  a  slide,  and  baked  as  described  for  full  sets.  The 
little  slip  of  platinum  kept  the  two  teeth  in  place.  The  work 
shrunk  somewhat ;  but  this  was  remedied  by  again  placing  the 
piece  upon  the  model  with  the  intervention  of  tissue  paper 
covered  with  a  thin  coating  of  body.  Into  this  I  pressed  the 
piece  till  it  occupied  its  true  place,  and  then  filled  in  again  with 
more  body  all  the  crevices  around  the  roots  of  the  teeth,  and 
rebaked. 

"  After  enameling,  if  the  work  has  been  carefully  and  skilfully 


506  MECHANICAL    DENTISTRY. 

done  upon  this  plan,  it  will  be  as  fine  a  piece  in  appearance  and 
fit  as  can  be  made.  It  may  then  be  soldered  to  a  gold  plate,  and 
the  little  strip  of  platinum  between  the  teeth  be  cut  out.  With 
the  body  and  gum  formerly  in  use  many  difficulties  were  en- 
countered from  discoloration  of  the  gum,  or  from  other  injuries 
incurred  in  soldering.  But  with  Roberts'  material,  these  are 
easily  avoided,  and  the  piece  can  be  treated  the  same  as  block 
or  single  gum  teeth.  In  partial  sets  on  entire  plates  of  platinum 
trouble  has  sometimes  been  experienced  by  the  enamel  giving 
way  upon  the  small  narrow  points  that  connect  the  teeth  with 
the  plate  by  the  shock  occasioned  in  biting,  consequently  I  have 
left  these  points  uncovered,  and  used  two  or  three  thicknesses  of 
platinum  to  give  greater  strength.  But  where  this  is  likely  to 
occur,  gold  plates  would  be  preferable,  if  nicely  adapted  with 
single  gum  teeth,  or  blocks  of  continuous  gum,  as  the  case 
might  require.  I  have  also  applied  continuous  gum  in  cases 
where  the  natural  teeth,  from  one  to  five  in  number,  were  left  in 
the  mouth,  by  making  the  plates  as  in  full  sets,  cutting  out 
around  the  natural  ones,  and  raising  a  small  bead,  or  placing  a 
light  wire  around,  about  one-eighth  of  an  inch  or  more  from  the 
teeth,  against  which  the  gum  or  body  is  to  be  finished.  The 
points  around  the  teeth  are  to  be  left  free,  in  order  to  be  bur- 
nished down  in  cases  of  imperfections  caused  by  the  difficulty  of 
obtaining  exact  impressions  in  these  places.  In  such  cases  I 
have  sometimes  formed  a  strong  standard  of  several  thicknesses 
of  platinum  fitting  closely  against  one  or  more  natural  teeth, 
leaving  a  loophole  through  which  to  run  a  gold  clasp  for  after- 
ward securing  the  artificial  set. 

"  I  have  also  secured  the  gold  to  the  standard  by  rivets  of 
platinum,  and  sometimes  by  two  or  three  gold  screws,  not  pro- 
viding, in  these  cases,  the  loophole.  These  methods  are  to  be 
preferred  to  using  solder  for  fastening  ;  for,  in  case  of  repair,  the 
clasps  are  easily  removed  without  leaving  any  foreign  substance  ; 
but  in  case  of  soldering,  however  carefully  they  maybe  removed, 
there  will  remain  some  alloy,  which  in  the  baking  heat  to  which 
the  piece  is  to  be  exposed  will  be  incorporated  with  the  platinum. 
Even  so  small  an  amount  of  silver  as  may  be  in  gold  coin  used 
for  solder  will  communicate  a  yellowish  tinge  to  the  gum,  spoil- 


DENTURES    WITH    CONTINUOUS    PORCELAIN    GUM.  507 

ing  the  whole  work.  Many  operators  in  their  early  practice 
experienced  this  result,  and  learned  that  no  alloys,  espe- 
cially of  silver  or  copper,  can  be  admissible  for  soldering  this 
work.  I  have  tried  platinum  clasps  without  success,  as  no  elas- 
ticity could  be  obtained,  and  therefore  would  not  hold  upon  the 
teeth.  Another  source  of  mischief  may  properly  be  noticed  in 
this  place.  In  baking,  especially  with  a  new  furnace,  or  with 
muffles  lately  renewed,  either  at  the  first  or  second  heat,  or  it 
may  be  enameling,  the  piece  is  sometimes  changed  in  its  texture 
and  color,  as  is  supposed  by  the  gases  present,  and  the  pheno- 
menon is  called  gassing  the  piece.  The  body  becomes  porous 
and  of  a  bluish  color.  When  this  occurs  there  is  no  remedy 
but  to  place  it  on  the  metallic  die,  remove  the  whole  of  the 
injured  part,  and  replace  it  with  a  new  coating  of  body  and  gum. 
The  teeth  are  seldom,  if  ever,  thus  affected..  As  a  precaution,  the 
muffles  should  be  well  ventilated  with  holes  for  the  passage  of 
the  heated  air  and  eases." 


CHAPTER  XIII 
RUBBER  OR  VULCANITE  BASE. 

While  there  are  undoubtedly  many  important  uses  to  which 
vulcanized  India-rubber  may  be  applied  in  the  practical  depart- 
ments of  dentistry,  and  for  which  it  would  be  difficult  to  find  an 
adequate  substitute,  yet  there  are  accumulating  evidences  leading 
to  the  conclusion  that  its  total  abandonment,  as  a  base  for  artifi- 
cial dentures,  by  intelligent  and  conscientious  practitioners  every- 
where, is  an  event  of  the  not  distant  future. 

This  anticipated  result,  in  respect  of  a  material  which  has  been 
almost  universally  employed  as  a  base  for  the  past  twenty  years, 
is  assured  by  the  confirmed  and  steadily  increasing  distrust  of 
its  suitableness  for  the  purpose  indicated,  and  the  growing  ten- 
dency in  the  profession  to  return  to  higher  and  less  objectiona- 
ble forms  of  substitution  as  respects  both  material  and  construc- 
tion. 

While  the  statements  made  in  former  editions  of  this  work  in 
regard  to  rubber  as  a  base  reflected,  as  the  author  believed, 
the  estimate  of  its  fitness  by  the  profession  generally,  what  is 
now  written,  we  believe,  embodies  the  present  judgment  of  the 
mass  of  enlightened  practitioners  in  reference  to  its  unsuitable- 
ness  and  the  necessity  of  its  abandonment  as  a  base.  While 
the  latter  is  a  consummation  "  devoutly  to  be  wished,"  there 
is  warrant  for  the  belief  that  the  time  when  the  use  of  the 
vegetable  plastics,  as  a  base,  will  be  discarded  will  be  con- 
tingent on  the  introduction  of  other  equally  inexpensive  methods 
of  substitution  that  are  wholly  free  from  the  confessed  and  well- 
grounded  objections  that  are  attached  to  both  rubber  and  cellu- 
loid. 

General  Properties  of  India-Rubber. — Caoutchouc,  gum- 
elastic,  or  India-rubber  exists  as  a  milky  juice  in  several  plants, 
but  is  extracted  chiefly  from  the  Siplioiiia  caliuca,  which  grows 
in    South    America    and    Java,     It    is    discharged  through  the 

508 


RUBBER    OR    VULCANITE    BASE.  5O9 

numerous  incisions  made  in  the  tree  through  the  bark,  and  is 
spread  upon  clay  molds,  and  dried  in  the  sun,  or  with  the  smoke 
of  a  fire,  which  blackens  it.  The  juice  when  first  obtained  is  of 
a  pale  yellow  color,  of  about  the  consistency  of  cream,  and  has 
a  specific  gravity  of  about  1.012.  In  the  process  of  drying  55  per 
cent,  is  lost,  the  residuary  45  being  elastic  gum.  It  immediately 
coagulates,  by  reason  of  its  albumin,  on  application  of  heat,  the 
elastic  gum  rising  to  the  surface.  The  specific  gravity  of  the 
juice  is  diminished  by  inspissation,  becoming  0.925  when  hard, 
and  cannot  be  permanently  increased  by  any  degree  of  pressure. 
When  once  stiffened  by  cold  or  continued  quiescences  it  cannot 
be  restored  to  its  original  condition  of  juiciness. 

The  inspissated  juice,  or  crude  rubber  of  commerce,  is  alto- 
gether insoluble  in  water  or  alcohol,  but  is  readily  soluble  in 
ether  deprived  of  its  alcohol  by  washing,  affording  a  colorless 
solution.  On  evaporation  of  the  ether,  the  gum  resumes  its 
original  condition.  It  swells  to  thirty  times  its  bulk  when  treated 
with  hot  naphtha,  and  if  triturated  in  this  condition  in  a  mortar, 
and  pressed  through  a  sieve,  furnishes  a  homogeneous  varnish 
employed  in  the  preparation  of  a  waterproof  cloth. 

Caoutchouc  is  soluble  in  the  fixed  oils,  but  is  not  readily 
decomposed  by  cold  sulphuric  acid  or  diluted  nitric  acid,  and  is 
unaffected  by  either  muriatic  acid  gas,  sulphurous  acid  gas,  fluo- 
silicic  acid,  ammonia,  or  chlorin,  nor  is  it  dissolved  by  the 
strongest  caustic  potash  lye,  even  at  a  boiling  heat,  and  is  there- 
fore highly  esteemed  as  an  appliance  of  the  chemical  laboratory. 
According  to  the  experiments  of  Ure,  Faraday,  and  others, 
caoutchouc  contains  no  oxygen,  as  almost  all  other  solid  vege- 
table products  do,  but  is  a  mere  compound  of  carbon  and  hydro- 
gen, in  the  proportion  of  three  atoms  of  the  former  to  two  of 
the  latter.  From  this  property  of  resisting  the  corrosive  action 
of  acid  vapors,  and  its  tenacity  of  adhesion  to  glass,  caoutchouc, 
when  melted,  forms  a  very  excellent  lute  for  chemical  appa- 
ratuses. 

Such  are  some  of  the  properties  of  this  remarkable  product, 
the  uses  of  which  have  been  almost  immeasurably  extended  since 
the  first  successful  efforts  to  produce  artificial  induration  by 
Charles  Goodyear  in  1844. 


510  MECHANICAL    DENTISTRY. 

Compounding  Rubber  for  Dental  Purposes. — India-rubber 
is  prepared  for  vulcanizing  by  incorporating  with  it,  in  varying 
proportions,  either  sulphur  alone  or  some  of  its  compounds, 
sulphur  being  an  essential  component  of  all  vulcanizable  gum 
compounds.  For  dental  purposes,  the  coloring  is  effected  in 
most  preparations  by  the  introduction  of  vermilion  (sulphuret 
of  mercury).  These  substances,  properly  combined,  are  sub- 
jected to  artificial  heat  for  a  specified  time,  producing  a  hard, 
hornlike  substance,  possessing  the  qualities  of  lightness, 
strength,  durability,  imperviousness  to  fluids,  insolubility  in  the 
oral  secretions,  unchangeableness  on  exposure  to  ordinary  tem- 
peratures, etc. 

Method  of  Constructing  an  Entire  Denture  in  a  Base  of 
Rubber. — As  the  manipulations  concerned  in  the  construction 
of  a  full  upper  set  differ  in  no  essential  respect  from  those  re- 
quired in  the  formation  of  a  denture  for  the  inferior  arch,  except 
as  the  two  differ  in  conformation,  requiring  corresponding  modi- 
fications of  practice  which  will  readily  suggest  themselves,  it 
will  be  sufficient  to  describe  the  method  of  constructing  an  entire 
denture  for  the  upper  jaw. 

An  impression  of  the  mouth  is  first  secured  in  the  usual  man- 
ner, and,  as  has  been  stated,  plaster-of-Paris  is  preferable  to  any 
other  material  for  the  purpose.  As  rubber,  when  rendered 
plastic  by  heat  and  subjected  to  pressure,  receives  a  distinct  and 
perfect  impress  of  the  face  of  the  model,  it  is  important  that  the 
latter  should  be  as  smooth  upon  its  surface,  and  as  free  from 
faultiness  of  form  or  surface  blemish,  as  possible.  From  the  im- 
pression a  plaster  model  is  obtained,  and  if  an  air-chamber  is 
required,  it  may  be  secured  either  by  cutting  out  from  the  im- 
pression before  filling  in  with  plaster,  for  the  model,  or  it  maybe 
raised  upon  the  model  after  the  latter  has  been  separated  from 
the  impression.  For  the  latter  purpose,  lead  is  often  used,  but 
sheet  tin,  cut  to  the  required  form,  is  preferable,  as  the  former 
leaves  a  tenacious  coating  of  oxid  adhering  to  the  plate. 

A  temporary  or  model  base-plate  is  next  conformed  as  ac- 
curately as  possible  to  the  face  of  the  model,  and  for  this  pur- 
pose the  prepared  giitta-percha,  paraffine  and  wax,  or  modeling 
compound  worked  into  thin  sheets  may  be  used,  or  a  die  may  be 


RUBBER    OR    VULCANITE    BASE.  5  I  I 

secured  and  a  trial  plate  struck  up  from  block  tin.  Though  the 
latter  requires  more  labor,  it  gives  more  satisfactory  and  accurate 
results.  The  former  may  be  softened  either  by  subjecting  them 
to  a  dry  heat  until  sufficiently  plastic,  or  by  immersing  in  hot 
water.  The  face  of  the  model  being  previously  well  saturated 
with  cold  water  to  prevent  the  wax  or  gutta-percha  from  adher- 
ing, the  latter  is  pressed  or  molded  accurately  to  the  model  with 
the  fingers  moistened  with  cold  water,  heating  such  portions 
from  time  to  time  as  do  not  readily  yield  to  pressure  until  an 
accurate  adaptation  of  all  portions  of  the  plate  is  secured  ;  then^ 
trim  to  the  required  dimensions. 

Having  fitted  the  temporary  plate  to  the  model,  it  is  placed 
in  the  mouth  with  a  wa.K  guide  or  rim  attached,  when  the  latter 
is  trimmed  to  the  required  width,  fullness,  and  contour,  and  the 
"bite"  of  the  under  teeth  secured;  it  is  then  removed  and 
placed  in  its  proper  position  on  the  model,  which  is  placed 
in  an  articulator,  with  the  antagonizing  model,  the  latter  being 
obtained  in  the  manner  described  in  connection  with  the 
metallic  plate-base  (page  417).  The  mode  of  procedure  in  cases 
of  entire  dentures  for  the  upper  and  lower  jaws  differs  in  no 
respect  from  that  practised  when  gold  or  other  metallic  plate  is 
used  as  a  base. 

Arranging  the  Teeth. — Having  secured  an  antagonizing 
model,  the  teeth  are  selected  and  arranged  upon  the  temporary 
plate  in  the  usual  manner.  The  porcelain  teeth  used  in  this 
process  are  more  commonly  in  the  form  of  blocks  or  sections. 
The  increased  strength  of  attachment  formed  by  the  greater 
number  of  pins  also  renders  them  more  permanent  and  endur- 
ing than  single  gum  teeth.  Teeth  made  expressly  for  rubber 
base  were  originally  manufactured  with  plain  platina  pins,  longer 
and  heavier  than  those  used  in  connection  with  metallic  plates 
(Fig.  513);  these,  when  used,  were  curved  and  pressed  together, 
forming  loops  or  hooks  to  prevent  them  withdrawing  from  the 
rubber.  Subsequently,  however,  the  detachment  of  the  teeth 
was  more  securely  and  certainly  provided  against  by  the  substi- 
tution of  headed  pins  (Fig.  514),  which  rendered  their  with- 
drawal from  the  rubber  impossible.  For  this  valuable  improve- 
ment  the  profession   is   indebted  to   the  late   Dr.  S.  S.  White, 


512 


MECHANICAL    DENTISTRY. 


whose  genius,   enterprise,  and  intelligence  were    so    long  and 
unceasingly  tributary  to  the  needs  of  the  dental  practitioner. 

Attention  has  already  been  called  to  Dr.  Land's  improvement 
in  teeth.     The  form  specially  adapted  to  rubber  work  is  shown 


Fig.  513. 


F"iG.  514. 


in   the  right-hand  cut,  Fig.   510,  and  also  in  the  single   tooth, 
same  figure. 

The  latest  design  in  the  construction  of  porcelain  teeth  is 
shown  in  Fig.  515  The  ba.se  of  the  tooth  is  countersunk,  with 
headed  pins  inclosed  within  the  cavity.     It  is  claimed  that  their 


close  conformity  in  contour  to  the  natural  organs  makes  them 
much  more  acceptable  to  the  tongue  than  teeth  backed  in  the 
ordinary  manner,  renders  articulation  easier  and  more  distinct, 
and  prevents  disclosure  of  artificiality  when  the  mouth  is  opened. 


RUBBER    OR    VULCANITE    BASE. 


DM 


In  addition  to  these  advantages,  they  allow  greater  facility  of 
adaptation  to  the  maxillary  ridge.  They  are  particularly 
adapted  to  rubber  base  with  celluloid  facing,  or  to  celluloid  base 
alone.  Other  forms  of  "plain  teeth "  are  placed  upon  the 
market,  and  when  they  can  be  employed,  more  artistic  results 
may  be  secured  than  is  possible  with  the  gum  teeth. 

Grinding  and  Jointing  the  Teeth. — In  arranging  the  teeth, 
portions  of  the  wax  rim  are  cut  away  to  form  a  bed  for  each 
tooth  or  block,  as  the  case  may  be,  grinding  from  the  base  of 
the  latter  and  from  their  proximate  edges  until  the  proper 
-position  is  assigned  to  the  teeth,  and  the  required  antagonism  is 
secured.  When  gum  teeth  are  used,  whether  single  or  in  the 
form  of  blocks,  they  should  be  united  to  each  other  laterally 
with  the  greatest  possible  accuracy,  to  prevent,  as  far  as 
practicable,  the  intrusion  of  the  gum  material  between  them. 
To  further  provide  against  this,  various  expedients  have  been 
resorted  to  with  the  view  of  cementing  or  packing  the  joints  in 
order  to  render  them  impervious  to  the  rubber.  The  substances 
usually  recommended  for  this  purpose  are  plaster  or  finely 
pulverized  silex  or  felspar  moistened  with  dilute  liquid  silex, 
os-artificial,  soluble  glass,  gold  or  tin  foil,  or  fusible  metal 
packed  into  the  joints,  etc.  Of  the  more  destructible  substances 
mentioned,  Professor  Wildman  very  justly  observes:*  "All  of 
these,  in  course  of  time,  will  yield  to  the  action  of  the  fluids  of 
the  mouth ;  and  then  the  ill-fitted  joints  will  be  receptacles  for 
soft  particles  of  food,  which  will  be  more  objectionable  than 
having  them  filled  with  good,  solid  rubber.  The  best  filling  is 
an  accurately  fitted  joint ;  when  so  made,  if  the  enveloping 
plaster  is  of  good  quality  and  properly  mixed,  and  no  undue 
force  is  used  in  bringing  the  section  of  the  flask  together,  there 
is  little  danger  of  the  rubber  insinuating  itself  into  the  joints." 
As  properly  remarked,  there  is  no  expedient  which  will  so 
certainly  and  effectually  exclude  the  rubber  as  close-fitting  joints, 
and  if  the  precaution  is  taken  to  secure  an  accurate  and  uniform 
coaptation  of  the  ground  surfaces  where  they  unite  in  front,  and 
the  "  enveloping  plaster  is  of  good  quality  and  properly  mixed, 

*  "  Instructions  in  Vulcanite,"  p.  19. 


514 


MECHANICAL    DENTISTRY, 


Fig. 


/ 


■'-^i 


and  no  undue  force  is  used  in  bring- 
ing the  sections  of  the  flask  together," 
there  will,  at  most,  be  but  a  very  thin 
film  of  rubber,  nearly  imperceptible  in 
the  finished  work,  and  wholly  so  in 
the  mouth.  To  better  effect  the  ob- 
ject stated,  the  writer  has  been  accus- 
tomed, when  uniting  porcelain  blocks, 
to  use  a  small  magnifying  glass, 
which  reveals  inaccuracies  of  coap- 
tation not  apparent  to  the  naked 
eye. 

The  teeth  having  thus  been  prop- 
erly united  and  arranged,  the  wax 
rim  supporting  them  on  the  lingual 
side  should  be  cut  away  and  carved 
with  heated  instruments,  especially 
designed  for  that  purpose,  as  repre- 
sented in  Fig.  516,  until  the  required 
form  and  fullness  are  obtained,  add- 
ing wax,  if  necessary,  to  the  palatal 
portion  of  the  plate,  making  it  just 
enough  thicker  than  that  required  in 
the  completed  set  to  compensate  for 
waste  in  the  process  of  final  finishing. 
Any  considerable  excess  of  material 
should  be  avoided,  since  it  will  not 
only  materially  increase  the  labor  ot 
dressing  the  vulcanized  plate,  but 
tend  to  induce  porosity  or  sponginess 
of  the  rubber  under  heat.  A  rim  of 
wax  should  also  be  extended  around 
the  front  and  lateral  borders  of  the 
plate,  overlapping,  somewhat,  the  ex- 
tremities of  the  gum  portions  of  the 
teeth.  Wax  used  for  the  purposes 
indicated  should  be  of  the  cleanest 
and  purest  varieties.     A  set  modeled 


RUBBER    OR    VULCANITE    BASE. 


515 


in  the  manner  described  will  present  the  appearance  represented 
in  Fig.  518. 

Flasking. — The  process  having  been  conducted  thus  far, — 
any  defects  in  the  arrangement  of  the  teeth  having  been  pre- 
viously corrected  upon  trial  of  the  plate  in  the  mouth, — the 
next  step  in  the  operation  is  the  formation  of  a  mold  or  matrix 
in  which  the  gum  material  is  packed  and  pressed  preparatory  to 
being  vulcanized.  In  forming  a  matrix,  a  vulcanizing  flask  is 
used,  the  various  parts  of  which  are  separately  represented  in 
Fig-  517.  The  lower  section  of  the  flask  is  first  filled  one-half 
or  two-thirds  full  of  plaster  mixed  with  water  to  the  consistency 
of  cream.     Into  this  the  base  of  the  model,  previously  moist- 

FiG.  517. 


ened  with  water  (the  plate  and  teeth  being  attached  to  the 
model),  is  immersed  and  additional  portions  of  the  plaster 
added,  if  necessary,  filling  the  cup  even  with  the  upper  edge,  and 
extending  it  up  the  sides  of  the  model  to  the  lower  edge  of  the 
external  rim  of  wax  attached  to  the  borders  of  the  gum  plate. 
The  base  of  the  model  should  be  cut  away,  so  that  when  placed 
in  the  flask  the  lower  edge  of  the  gum  plate  will  extend  but  little 
above  the  level  of  the  upper  borders  of  the  cup.  The  surface 
of  the  plaster  is  then  trimmed  smoothly,  and  coated  with  varnish 
and  then  oiled ;  all  the  exposed  portions  of  the  gum  plate  and 
wax  are  also  oiled,  leaving  the  sui^faces  of  the  teeth  untouched. 
The  several  parts  will  now  present  the  appearance  represented 


Si6 


MECHANICAL    DENTISTRY, 


in  Fig.  518.  The  upper  section  of  the  flask  is  next  placed  in 
its  proper  position  over  the  lower — the  slides  formed  in  one, 
and  corresponding  grooves  in  the  other,  determining  an  accurate 
relation  of  the  two  pieces.  Into  the  upper  rim  of  the  flask, 
plaster,  mixed  to  the  consistency  before  mentioned,  is  now 
poured,  filling  it  completely.  The  lid  or  cap  is  then  applied  to 
the  opening  above,  and  the  several  parts  of  the  flask  brought 
firmly  together,  forcing  the  excess  through  the  joints  of  the  flask. 
As  soon  as  condensation  of  the  plaster  takes  place,  the  flask 
should  be  placed  in  a  hot-air  chamber  or  on  a  stove,  and  heated 

Fig.  518. 


throughout  just  sufficiently  to  soften,  but  not  viclt  the  ivax.  The 
two  sections  of  the  flask  are  then  carefully  separated  by  forcing 
the  blade  of  a  knife  or  a  small  chisel-shaped  instrument  in  at 
different  points  between  them,  the  lid  closing  the  opening  above 
remaining  in  place.  On  separating  the  flask,  the  teeth,  with  the 
wax  and  temporary  plate,  will  be  found  attached  to  the  section 
of  the  matrix  last  formed,  the  portions  of  the  crowns  of  the  teeth 
not  covered  with  wax  being  embedded  in  the  plaster  and  their 
plate  extremities  presenting  toward  the  matrix*,  as  seen  in  Fig. 
519.  The  base  plate  and  wax  should  now  be  carefully  detached 
with  such   instruments  as  will   best  enable  the  operator  to  work 


RUBBER    OR    VULCANITE    BASE. 


517 


out  confined  portions  around  the  platinum  pins  and  from  the  in- 
terstices between  the  teeth,  being  careful  at  the  same  time  not  to 
deface  the  plaster  surface  of  the  mold.  To  relieve  the  matrix 
more  perfectly  of  all  traces  of  wax  not  accessible  to  instruments, 
the  section  containing  the  teeth  may  be  subjected  to  a  heat  suffi- 
cient to  induce  its  complete  absorption  by  the  plaster.  The  flask 
should  be  heated  gradually,  otherwise  the  contents  may  be  sud- 

FiG.  519. 


denly  and  forcibly  ejected,  in  consequence  of  the  too  rapid  evo- 
lution of  vapor. 

Before  packing  the  material,  provision  should  be  made  for  the 
escape  of  any  excess  when  the  matrix  is  filled  and  the  two  sec- 
tions of  the  flask  are  forced  together,  permitting  the  latter  to  close 
upon  each  other  in  exactly  the  same  manner  as  before  the  intro- 
duction  of  the    crum.     If  the   vulcanizable   substance   becomes 


5l8  MECHANICAL    DENTISTRY. 

engaged  between  the  surfaces  of  the  plaster  around  the  matrix, 
the  vulcanized  base  will  be  increased  in  thickness  just  in  propor- 
tion to  that  of  the  interposed  layer  of  gum,  and  hence  the  teeth 
of  replacement  will  be  relatively  elongated.  This  increased 
thickness  of  the  base  and  consequent  changed  relation  of  the 
teeth  to  the  maxillary  ridge  and  to  those  of  the  opposing  jaw, 
if  but  slight,  may  be  immaterial  in  the  application  of  full  sets  of 
teeth  ;  but  it  is  far  different  in  the  construction  of  partial  pieces, 
where  the  perfection  of  the  finished  work  depends  in  so  great  a 
degree  upon  a  faultless  preservation  of  the  exact  position  origi- 
nally assigned  to  the  organs  of  replacement  in  the  several  vacui- 
ties on  the  ridge.  If,  for  example,  in  replacing  the  superior  in- 
cisors, the  approximation  of  the  two  sections  forming  the  mold 
is  obstructed  by  the  intrusion  of  the  gum  material  between  the 
plaster  surfaces,  the  teeth,  whether  plate  or  gum,  will  be  rela- 
tively elongated  in  proportion  to  the  increased  thickness  im- 
parted to  the  base  consequent  upon  the  incomplete  closure  of 
the  flask,  and  however  accurately  or  skilfully  the  porcelain  teeth 
may  have  been  originally  fitted  to  the  vacuity  in  front,  the  artifi- 
cial will  be  found  to  depart  from  the  natural  gum,  while  the 
porcelain  crowns  will  be  displaced  and  projected  below  those  of 
the  contiguous  natural  organs.  Such  displacement  in  the  cases 
last  referred  to,  however  small  in  degree,  cannot  fail  either  to 
impair  or  destroy  the  value,  both  as  respects  appearance  and 
utility,  of  the  substitute.  The  method  of  furnishing  an  exit  to 
redundant  material,  as  usually  practised,  is  to  form  a  series  of 
conduits  or  grooves  in  the  surface  of  the  plaster,  extending  them 
from  the  edge  of  the  matrix  to  the  rim  of  the  cup.  The  escape 
of  the  gum  will  be  facilitated  by  cutting  notches  at  intervals 
around  the  rim  of  the  flask,  making  the  grooves  in  the  plaster 
continuous  with  them,  the  grooves  being  an  eighth  or  a  fourth 
of  an  inch  apart.  To  still  more  effectually  prevent  the  intrusion 
of  the  vulcanite  material  between  the  surfaces  of  the  opposing 
sections  of  plaster,  a  circular  groove  may  be  cut  in  the  plaster 
within  a  line  or  two  of  the  margins  of  the  matrix,  as  is  shown 
in  the  illustration.  Fig.  520,  into  which  narrow  channels  at  short 
distances  are  made,  leading  from  the  mold ;  others,  again,  are 
made  at  wider  intervals  from  the  circular  eroove  to  the  outer 


RUBBER  OR  VULCANITE  BASE. 


519 


margins  of  the  flask,  terminating  as  before  |in  small  notches 
formed  in  the  rim  of  the  cup.  The  two  pieces  when  closed 
upon  each  other  form  a  matrix.  Into  the  grooved  section  of  the 
mold,  the  vulcanizable  substance  is  packed  previous  to  being 
indurated.  It  is  at  this  stage  that  the  materials  employed  to 
e.Kclude  the  rubber  from  between  the  teeth,  and  noticed  in 
another  place,  are  packed  into  the  joints  before  the  gum  material 

Fig.  520. 


is  introduced.  The  face  of  the  model  should  also  be  coated 
with  some  substance  which  will  prevent  the  rubber  from  pene- 
trating the  pores  of  the  plaster  and  its  adhesion  to  the  surface 
of  the  model.  Preference  is  given  by  Professor  Wildman  to 
liquid  silex,  as  being  more  readily  detached  from  the  surface  in 
finishing  than  the  preparations  mentioned.  Whatever  is  used, 
it  should  be  allowed  to  dry  perfectly  before  packing.  Other 
methods,  and  good  ones,  are  to  burnish  a  sheet  of  tinfoil  over 


520  MECHANICAL    DENTISTRY. 

the  cast,  or  sprinkle  Lycopodium  or  soapstone  upon  the  surface 
of  the  cast.  These  latter  should  be  brushed  off  with  a  jeweler's 
brush  or  a  soft  brush  wheel,  which  will  leave  the  surface  of  the 
model  with  a  high  polish. 

Packing  the  Mold. — The  portion  of  the  flask  containing  the 
teeth  should  be  first  heated  in  an  oven  or  furnace,  or  over  the 
flame  of  a  spirit-lamp,  until  the  temperature  of  the  whole  is  suffi- 
cient to  render  the  rubber  soft  and  pliable  as  successive  portions 
are  applied  and  pressed  into  the  mold,  and  to  retain  it  in  that 
condition  until  the  operation  of  packing  is  completed.  Narrow 
strips  of  the  rubber  should  first  be  worked  carefully  into  the  con- 
tracted groove  underneath  the  platinum  pins  with  small  curved 
or  straight-pointed  spear-shaped  steel  instruments  (Fig.  521), 
adding  on  small  pieces  at  a  time  after  each  successive  portion  is 
thoroughly  impacted,  until  the  main  groove  of  the  matrix  over 
the  base  of  the  teeth  is  partially  filled.     The  palatal  convexity 

Fig.  521. 


of  the  mold  may  then  be  covered  with  a  single  piece  cut  to  the 
form  of  the  uncovered  space  ;  a  smaller  piece  of  the  same  general 
form  as  the  latter  may  then  be  added,  giving  to  the  central  por- 
tion a  double  thickness  of  the  gum-plate  material,  so  that  when 
the  two  sections  of  the  flask  are  brought  together  the  excess  of 
gum  in  the  center  will  be  forced  gradually  to  the  margins  of  the 
mold,  diminishing,  thereby,  the  liability  of  the  grooves  becoming 
prematurely  clogged  with  the  material  before  the  opposing  sec- 
tions of  the  flask  close  upon  each  other.  Especial  care  should 
be  taken  in  the  process  of  packing  to  avoid  contact  of  the  instru- 
ments with  the  surface  of  the  mold,  as  fragments  of  the  broken 
plaster  are  liable  to  mix  with  the  gum  and  render  the  surface  of 
the  finished  work  imperfect  by  forming  small  pits  wherever  such 
particles  occur. 

In  regard  to  the  quantity  of  rubber  necessary  to  perfectly  fill 
the  matrix,  experience  in  its  use  will  enable  the  operator  to  esti- 


RUBBER    OR    VULCANITE    BASE. 


521 


mate  the  capacity  of  the  mold  with  tolerable  accuracy.  Some 
small  excess  of  rubber  should  always  be  provided.  The  required 
quantity,  however,  can  be  more  certainly  determined  by  uicasurc- 
ment.  A  very  simple  instrument  (Fig.  522),  contrived  by  Dr.  E. 
T.  Starr,  maybe  used  to  determine  the  quantity  by  measurement. 


The  vessel  being  partly  filled  with  water,  the  lower  point  is 
adjusted  and  fixed  with  a  screw  to  mark  its  height.  Into  this 
every  particle  of  the  model  plate  is  immersed,  and  the  rise  of 
water  indicated  in  the  same  manner  by  the  upper  point.  The 
vessel  is  then  emptied  and  well  cleansed,  clean  water  filled  in  to 
the  level  of  the  lower  point,  when  rubber  is  added  in  sufficient 


522 


MECHANICAL    DENTISTRY. 


quantity  to  bring  the  surface  of  the  water  on  a  level  with  the 
upper  point ;  to  this  is  to  be  added  the  necessary  excess  of  rub- 
ber before  recommended. 

Having  completed  the  packing  of  the  mold,  the  two  portions 
of  the  flask  are  re-applied  to  each  other  in  exactly  their  original 
relation,  being  careful  that  the  apposition  of  the  two  is  such  that, 
when  approximated,  the  guides  attached  to  one  division  of  the 
flask  shall  pass  directly  and  without  obstruction  into  the  grooves 
or  slots  in  the  one  opposite.  With  the  flasks  first  introduced, 
some  difficulty  and  uncertainty  were  experienced  in  effecting 
the  desired  closure  of  the  flask  on  account  of  inherent  defects 
of  construction,  but  more  recent  improvements  have  entirely 
obviated  this  difficulty.     Fig.  523   represents  the   Hayes  flask, 


Fig.  523. 


Fig.  524. 


with  improved  clamps.  The  lug-joint  is  so  constructed  that  the 
strain  all  comes  upon  the  casting.  The  pin  only  serves  to  keep 
the  lug  in  place  while  not  in  use.  The  several  pieces  all  being 
attached  together,  are  not  liable  to  get  lost  or  mislaid.  The 
improved  Whitney  flask  is  shown  in  Fig.  524.  The  improve- 
ment in  construction  consists  in  reversing  the  position  of  the 
bolts,  fitting  the  head  into  the  hole  in  the  lower  part  of  the  flask, 
and  using  a  nut  on  top. 

What  is  known  as  the  "  Starr  Flask,"  highly  commended  as 
fulfilling  very  perfectly  the  requirements  of  practice,  and  as 
happily  meeting  some  important  indications,  is  represented  in 
Fig-  525.  Every  operator  of  experience  is  familiar  with  the 
annoyance  and  difficulty  sometimes  attending  a  satisfactory 
adjustment  of  models  of  unusual  depth,  often  of  lower  sets,  and 


RUBBER  OR  VULCANITE  BASE. 


52; 


partial  pieces,  where  the  porcelain  teeth  are  secured  by  the 
surrounding  plaster  to  the  model — difficulties  arising  from  the 
shallowness  of  the  lower  section  of  flasks  as  ordinarily  con- 
structed. The  "  Reversible  Flask,"  invented  by  Dr.  E.  T. 
Starr,  the  different  parts  of  \vhich  are  represented  in  the  accom- 
panying cut,  provides  very  perfectly  for  any  exigency  that  may 
arise  in  the  class  of  cases  mentioned.  The  following  descrip- 
tion of  this  flask  is  taken  from  the  Dental  Cosmos  : — 

Fig.  525. 


"  The  rings  of  this  flask  are  of  different  widths,  either  of  them 
fitting  the  top  or  bottom  accurately,  as  may  be  required. 

"  By  using  the  wide  ring  next  to  the  bottom,  an  admirable 
flask  is  obtained  for  deep  cases  and  partial  sets,  or  where  the 
artificial  gum  rests  on  the  natural.  The  narrow  ring  is  used 
next  the  bottom  plate,  for  whole  dentures,  where  the  parting  is 
at  the  rirn  of  the  plate.  The  bottom  has  three  countersunk 
holes,  through  which  the  plaster  runs,  and,  when  set,  holds  the 


524 


MECHANICAL    DENTISTRY 


accompanying  ring  securely  to  it.  The  fastenings  of  the  flask 
are  T-shaped  at  one  end,  and  fit  the  slots  in  the  bottom  plate ; 
and,  being  free  at  both  ends,  are  more  easily  adjusted  than 
ordinary  bolts.  The  flask  being  in  four  pieces  (two  rings  and 
two  plates),  the  plaster  is  removed  without  the  usual  trouble. 
Fig.  525  represents  the  flask  in  sections." 

The  writer  has,  for  several  years,  used  almost  exclusively,  and 
with  the  greatest  satisfaction,  a  flask  constructed  with  detached 
T-shaped  bolts  fitting  accurately  into  slots  or  grooves  extending 
continuously  from  top  to  bottom  of  the  flask,  as  represented  in 
Fig.  526.  The  closure  of  the  sections  by  this  arrangement, 
with  the  bolts  in  place,  is  unerring,  and  is  accomplished  with 

Fig.  526. 


the  greatest  facility.  It  is  known  as  the  "  Improved  Anchor 
Flask,"  and  is  manufactured  by  Gideon  Sibley,  of  Philadelphia. 

The  "Taylor  Improved  Flask"  is  represented  in  Fig.  527. 
The  posterior  and  lateral  portions  of  the  lower  section,  having 
raised  margins,  gives  the  section  at  these  points  considerable 
additional  depth,  a  modification  of  form  especially  well  adapted 
to  lower  pieces.  Still  another  useful  form  of  flask  is  that 
devised  by  Dr.  I.  N.  Broomell,  and  is  represented  in  Fig.  528. 

Fig.  529  represents  an  oblong,  or  "box  flask,"  designed  for 
exceptionally  large  cases,  splints  for  fractures,  artificial  palates, 
etc. 

Whatever  flask  is   used,  the  entire  mass   of  inclosed  rubber 


RUBBER    OR    VULCANITE    BASE. 


525 


Fig.  527. 


Fig.  528. 


should  be  rendered  uniformly  plastic,  after  packing,  by  subject- 
ing it  to  either  a  dry  heat,  such  as  may  be  obtained  with  a 
conveniently  constructed  sheet-iron  furnace,  the  baking  apart- 


526 


MECHANICAL    DENTISTRY. 


merit  of  an  ordinary  cooking  stove,  or  any  other  available 
means  by  which  a  diffused  and  uniform  temperature  may  be 
secured,  being  careful  not  to  overheat;  or,  if  moist  heat  is 
employed,  by  immersing  the  flask  in  boiling  water  for  a  time 
sufficient  to  soften  the  rubber.  The  approximation  of  the 
sections  of  the  flask  should  be  effected  interruptedly — alter- 
nately heating  the  entire  mass  and  tightening  by  means  of  the 
screw-bolts  until  all  the  redundant  material  is  expelled  by 
degrees  through  the  outlets  provided  for  it,  and  the  sections  of 
the  flask  close  accurately  upon  each  other. 

Fig.  520. 


Vulcanizing. — The  process  of  vulcanizing  or  hardening  the 
various  rubber  compounds  employed  for  dental  purposes  is 
effected  by  subjecting  them  for  variable  periods  of  time  to  the 
action  of  heat,  the  substances  to  be  acted  on  being  confined 
within  a  chamber  constructed  for  the  purpose. 

As  introductory  to  a  consideration  of  the  usual  methods  and 
appliances  employed  in  the  process  of  vulcanizing,  considerable 
space  is  given  to  the  following  somewhat  lengthy  abstract  of  a 
paper  by  F.  Alb.  Boeck,  of  Berlin,  Germany,  translated  by  Dr. 
Louis   Ottofy,  of  Lebanon,  111.*     The    discussion    embodies    a 

*Missoitri  Dental  Journal,  June  and  August,  1882. 


RUBBER  OR  VULCANITE  BASE.  52/ 

somewhat  exhaustive  consideration  of  the  rationale  of  the  pro- 
cess of  vulcanizing,  and  is  introduced  in  this  connection  not  only 
as  a  matter  of  curious  scientific  interest,  but  of  practical  import- 
ance in  the  proper  treatment  of  a  plastic  material  which  still 
continues  to  be  largely  used  as  a  base  for  artificial  dentures. 
The  writer  says  : — 

"The  rubber  we  use,  as  is  well  known,  is  common  rubber 
mixed  with  sulphur,  to  which  is  added  certain  coloring  materials. 
Of  the  latter  I  will  speak  later  in  the  course  of  this  paper. 
Though  they  may  influence  the  hardening  of  the  rubber  indi- 
rectly, they  have  no  other  direct  influence.  This  rubber  mixed 
Avith  sulphur  forms  our  '  dental  rubber.'  The  rubber  which  we 
obtain  from  the  dental  depots  is  already  '  vulcanized,'  as  this 
latter  simply  means  mixing  the  sulphur.  We  know  that  when 
it  is  heated  it  becomes  hard.  The  circumstances  under  which 
this  takes  place  leads  us  to  several  questions  :  Is  it  the  heat,  or 
the  steam  pressure,  or  the  melting  of  the  sulphur,  which  causes 
the  change  in  the  rubber. 

"Formerly,  the  impression  prevailed  that  the  hardening  took 
place  from  the  influence  of  the  steam.  In  the  first  vulcanizers 
the  flask  stood  on  a  stand  in  the  vulcanizers  above  the  water ; 
but  as  once,  in  1856,  the  flask  fell  into  the  water,  the  vulcanizing 
took  place  as  usual,  the  mistake  was  corrected.  Later  it  was 
found  that  the  process  would  take  place  even  if  the  heat  was 
passed  through  oil'or  sand,  and  that  the  same  was  the  case  with 
glycerin  and  paraffin.  Certainly,  under  these  circumstances,  the 
time  of  vulcanizing  was  longer  than  when  steam  was  used  ;  this 
circumstance,  at  that  time,  however,  was  of  no  particular  conse- 
quence, as  it  took  from  three  to  four  hours  to  vulcanize  it  by 
steam.  I  will  return  to  this  difference  of  time  later;  suffice  it  to 
state  here  that  vulcanizing  can  take  place  in  the  absence  of 
steam. 

"  It  is  clear,  therefore,  that  it  is  the  heat  alone  which  causes 
the  hardening  of  the  rubber.  In  order  to  answer  the  question 
of  why  this  takes  place,  it  will  be  necessary  to  turn  into  the 
domain  of  chemistry. 

"  The  rubber  is  a  vegetable  product ;  it  is  the  sap  of  certain 
trees,  which   hardens   on  exposure  to  the  air.     As  a  vegetable 


528  MECHANICAL    DENTISTRY. 

product  it  is  liable  to  the  changes  of  all  other  vegetable  sub- 
stances, and  all  changes  which  it  undergoes  are  found  equally 
effective  on  other  vegetable  substances.  From  this  fact  it  is 
very  simple  to  draw  conclusions  for  our  purpose. 

"  Chemistry  teaches  that  all  vegetable  products,  such  as  wood, 
starch,  the  leaves  and  sap  of  plants,  consist  of  four  elements, 
oxygen,  nitrogen,  hydrogen,  and  carbon.  In  no  plant,  or  the 
product  of  a  plant,  is  carbon  absent,  and  it  is  mostly  in  connec- 
tion with  hydrogen  and  oxygen,  whereas  nitrogen  is  but  seldom 
present.  From  these  few  elements  nature  has  produced  all  that 
earth  possesses  of  vegetable  growth,  the  variety  and  difference 
being  sometimes  only  the  different  proportion  of  union  of  the 
elements,  or  the  addition  of  a  small  amount  of  acids,  bitter  sub 
stances,  coloring  matters,  or  salts.  Rubber  consists  only  of  the 
above  elements,  namely,  CisHy ;  it  belongs,  therefore,  to  the 
class  known  as  the  hydrocarbons,  and  to  that  class  of  these  in 
which  C  predominates.  It  is  interesting  to  notice  here  that  the 
change  from  the  soft  to  the  hard,  as  is  the  case  with  rubber,  is 
the  property  of  all  vegetable  products.  We  know  that  the  change 
takes  place  by  the  application  of  heat,  that  hydrogen  sulphid 
(HgS)  is  formed,  and  that  the  process  takes  place  during  the  ex- 
clusion of  air.  This  process  is  chemically  the  same  as  takes 
place  in  the  dry  distillation  of  wood,  in  the  changing  of  wood 
into  coal,  and  of  resin  into  amber.  If  wood  is  heated  in  the 
open  air  it  burns  ;  the  same  is  the  case  with  rubber,  only  that 
the  latter  burns  slower  on  account  of  its  larger  percentage  of  C. 
If  wood  is,  however,  heated  in  the  absence  of  air,  as  is  the  case 
in  making  illuminating  gas,  quite  peculiar  substances  are  elimi- 
nated from  the  wood,  the  illuminating  gas,  which  escapes,  and 
three  substances ;  a  watery  pyroligneous  acid  (wood  vinegar), 
a  thick,  viscid  liquid  (wood  tar),  and  a   solid  mass  (charcoal). 

"The  wood  tar  is,  like  the  rubber,  of  a  resinous  nature;  it 
consists  of  the  oil  of  wood  tar  and  a  liquid  substance,  burnt  resin. 
Both  become  hard  on  cooling ;  the  former  is  the  well-known  par- 
affin, the  latter  the;  equally  well-known  pitch. 

"  The  rubber  undergoes  similar  changes.  If  it  is  heated  while 
excluded  from  the  air,  as  is  the  ca:se  in  vulcanizing,  there  escapes 
(as  in  the  case  of  wood,  illuminating  gas),  the  hydrogen  sulphid. 


RUBBER  OR  VULCANITE  BASE.  529 

and  there  remains  a  plastic,  which  hardens  on  coohng,  as  in  the 
case  of  pitch  or  paraffin,  and  we  have  our  hard  rubber. 

"  If  we  think  over  this  subject,  it  becomes  clear  to  us  why 
sulphur  is  added  to  the  rubber.  By  dry  distillation  one  or  more 
equivalents  of  hydrogen  separate  from  the  mass  and  remain 
gaseous,  or  unite  with  other  substances  present  and  form  a  liquid, 
thus  leaving  behind  a  hard  substance,  which  consists  mainly  ot 
C.  It  is  well  known  that  the  hardest  substance,  the  diamond,  is 
pure  C.  The  more  equivalents  of  H  that  remain,  the  softer  is 
the  substance,  as  in  the  following  scale  :  coal,  resin,  pitch,  axle 
grease,  oil,  ethereal  oils,  gases.  The  same  is  the  case  in  the  re- 
versed order.  If,  from  the  soft  rubber  hard  rubber  is  to  be 
made,  it  is  necessary  to  remove  from  it  one  or  more  equivalents 
of  H.  This  is  the  case  in  dry  distillation.  If  there  was  no  dry 
distillation,  if  the  rubber  was  heated  under  free  admission  of  air, 
the  C  would  immediately  unite  with  the  O  of  the  air,  forming 
carbonic  acid,  combustion  would  take  place,  even  though  it 
would  be  slow  and  difficult.  That  cannot  take  place  when  the 
air  is  excluded,  the  carbon  remains  unchanged,  whereas  the  H 
finds  a  substance  with  which  it  is  more  than  willing  to  unite  at  a 
high  temperature.  This  substance  is  the  S,  and  the  union  of 
these  forms  HgS,  which  is  well-known  to  us  by  its  odor.  When 
this  union  has  taken  place  a  chemical  change  has  been  accom- 
plished, a  new  substance  has  been  produced,  the  gas  escapes, 
the  remainder,  the  product  of  the  distillation,  contains  less  H 
than  the  raw  rubber,  and  on  coolmg,  like  pitch,  it  becomes  a 
harder  substance  by  its  containing  more  C  than  before.  Hard 
rubber,  therefore,  is  one  step  nearer  to  resin  than  soft  rubber. 
All  resins  are,  as  is  well  known,  involatile  substances,  and  they 
possess  the  power  to  prevent  other  substances  from  becoming 
volatile  ;  they  are  insoluble  in  water,  and,  consequently,  taste- 
less ;  they  are  soluble  in  volatile  oils,  as  turpentine  oil,  benzene, 
etc.  It  is  known  that  hard  rubber  does  not  only  possess  these 
characteristics,  but  resembles  the  resins,  by  its  easy  electrifica- 
tion, to  a  remarkable  degree. 

"  My  hypothesis,  therefore,  leads  me  to  the  following  conclu- 
sion : — 

"  Tlie  hardening,  or  so-called  vulcanizing  of  rubber,  is  the  cJiang- 
34 


530  MECHANICAL    DENTISTRY. 

ing  of  caoutchouc  into  a  resi)i-rcsembli)ig  substance,  by  the  process 
of  dry  distillation ;  that  is,  by  the  removal  of  one  equivalent  of 
H.  The  addition  of  S  serves  only  as  a  base,  which  is  indifferent 
toivard  C,  but  unites  zvith  H  by  virtue  of  a  strong  chemical  affinity 
existing  between  H  and  S,  which  form  a  new  compound,  H2S, 
zvhich  escapes  as  a  gas. 

"  You  will  notice  I  do  not  agree  with  the  opinion  that  the 
sulphur,  by  melting  and  hardening,  exerts  the  influence  required 
to  harden  the  rubber.  The  hypothesis  was  laid  down  in  some 
American  dental  journal,  that  just  as  is  the  case  with  camphor 
and  celluloid,  it  is  with  sulphur  and  rubber — that  is,  that  the 
sulphur  is  the  medium  which  brings  the  particles  of  rubber  into 
the  plastic  condition,  and  afterward  retains  them  in  the  hardened 
condition. 

"  We  know  that  a  portion  of  the  original  composition  of  the 
rubber  has  disappeared,  and  we  know  that  some  of  the  sulphur 
and  hydrogen  disappear.  It  is  natural  that  if  more  sulphur  is 
present  than  can  combine  with  one  equivalent  of  hydrogen,  the 
remainder  is  in  mechanical  union  with  the  rubber.  If  hard  rub- 
ber be  heated  to  a  degree  somewhat  higher  than  the  boiling 
point  of  water,  it  loses  its  hardness.  This  fact  might  lead  to  the 
conclusion  that  the  sulphur  melts,  and  thus  influences  the  hard- 
ness of  the  rubber.  If,  however,  the  correctness  of  my  theory  be 
granted — that  is,  that  hard  rubber  is  nothing  but  the  resinous 
state  of  the  original  product — we  observe  that  it  must  soften,  as 
the  melting  point  of  the  resins  is  about  the  same  as  that  of  sul- 
phur. Furthermore,  we  know  that  sulphur  hardens  slowly, 
whereas  resins  become  hard  more  rapidly,  as  is  the  case  with 
shellac  and  sealing  wax ;  the  same  is  the  case  with  heated  hard 
rubber.  Hard  rubber,  when  undergoing  the  change  from  its 
melted  condition  into  the  hard  condition,  does  not  change  the 
character  of  its  molecular  relation,  remaining  amorphous  ;  resem- 
bling in  its  structural  appearance  molten  glass.  All  resins,  gum, 
glue,  tar,  etc.,  show  the  same  characteristics.  Sulphur,  on  the 
contrary,  when  changing  from  its  molten  condition,  either  crys- 
tallizes or  becomes  crystalline  in  appearance. 

"  I  do  not  wish  to  prove  anything  further  by  this  theory.  It 
may,  however,  be  mentioned,  that  if  it  be  correct,  some  impor- 


RUBBER    OR    VULCANITE    BASE.  53! 

tant  results  may  be  accomplished.  I  will  mention,  for  one,  the 
fact  that  the  scraps  and  filings  of  hard  rubber,  which  are  now 
useless  and  thrown  away,  may  be  made  valuable  and  useful. 
Lately,  a  patent  has  been  obtained  by  which  useless  vulcanized 
rubber  may  be  made  useful. 

"  Leaving  this  subject,  we  now  arrive  at  one  not  less  import- 
ant, namely,  the  influence  of  steam  pressure  on  vulcanization. 

"  It  has  been  previously  stated  that  vulcanized  rubber  may  be, 
hardened  without  steam.  This  teaches  us  that  hardening  is  not 
produced  by  steam.  The  theory  which  has  been  discussed  gives 
us  the  reason.  The  question  arises.  Why  do  we  use  steam  ? 
The  ansv/er  is,  steam  has  no  direct  influence  in  vulcanizing ;  it 
only  serves,  the  same  as  oil,  sand,  parafiin,  or  glycerin,  for  the 
transmission  of  the  heat.  This  takes  place  by  use  of  steani, 
faster  and  with  more  precision  and  certainty  than  with  other 
substances.  Furthermore,  it  will  be  shown  further  on  that  for 
other  reasons  steam  is  the  best  vehicle  for  the  purpose. 

"As  with  oil,  by  using  steam  the  heat  is  equally  distributed 
and  the  temperature  rises  evenly.  Changes  of  temperature,  as 
is  the  case  in  dry  vulcanization  or  over-heated  steam,  are  also 
prevented.  It  also  has  the  important  advantage  of  causing  the 
hardening  to  take  place. more  rapidly.  This  latter  fact  is  known 
to  us  by  experience  ;  it  only  remains  to  explain  the  reason  why 
this  is  so. 

"  By  the  use  of  steam,  hardening  takes  place  in  from  fifteen 
to  seventy-five  minutes,  according  to  the  temperature,  the  quality 
of  the  rubber  and  its  thickness  ;  by  the  use  of  dry  heat  or  oil 
the  process  requires  from  two  to  three  hours,  and  the  requisite 
degree  of  heat  must  be  reached  gradually.  What  is  the  reason 
that  by  use  of  steam  and  a  high  degree  of  heat  it  takes  less 
time  to  vulcanize?  It  must  be  remembered  that  the  higher  the 
temperature  the  less  time  is  required  to  vulcanize.  The  reason 
of  this  is  clear,  if  we  remember  that,  according  to  my  theory, 
hardening  is  subservient  to  the  escape  of  a  certain  amount  of 
hydrogen  from  the  rubber. 

"The  greater  the  heat,  the  easier  is  the  separation  of  the  un- 
natural union — as  it  were — of  the  hydrogen  with  the  carbon  of 
the  rubber,  and  it  also  facilitates  the  union  of  this  H  with  the  S, 


532  MECHANICAL    DENTISTRY. 

which  is  in  a  molten  condition.  This  takes  place  in  accordance 
with  the  laws  of  chemical  affinity  and  relation.  It  is  a  sort  of 
magnetic  power  which  the  sulphur  exerts  upon  the  hydrogen, 
and  which  becomes  firmer  and  more  powerful  the  higher  the 
temperature.  Here  the  steam  does  not  take  any  part,  as  it  only 
does  the  same  thing  that  oil  or  sand  would  do,  and  that  is  to 
transmit  the  heat.  There  must  be  another  reason  why  the  use 
of  steam  permits  us  to  increase  the  temperature  and  shorten  the 
time.  We  know  that  we  cannot  do  so  when  using  sand  or  oil, 
as  in  that  case  the  rubber  becomes  porous.  If  we  can  find  the 
reason  why  the  rubber  becomes  porous,  we  can  ascertain  the 
influence  of  the  steam  when  used  a  shorter  time. 

"A  great  deal  has  been  written  and  said  in  regard  to  the  por- 
ousness of  rubber.  This  takes  place  when  the  escape  of  the  gas 
is  retarded  or  prevented  in  certain  places.  This  may  take  place 
when  the  heat  was  applied  rapidly  or  unevenly,  or  when  it  was 
not  equally  distributed  to  all  parts  of  the  rubber.  In  the  latter 
case,  such  parts  as  are  more  exposed  to  the  radiating  heat  than 
others  become  hard  much  sooner,  because  the  H  escapes  quicker. 
In  the  former  case,  that  is,  by  rapid  increase  of  heat,  the  outer 
surface  of  the  rubber  hardens  sooner  than  the  inner,  to  which 
the  heat  only  reaches  gradually.  Rubber  is,  as  is  well  known, 
the  poorest  of  conductors.  It  is  clear,  therefore,  that  the  thicker 
a  piece  is,  the  longer  it  takes  it  to  become  heated  in  all  parts, 
and  the  more  gradual  must  be  the  heating,  in  order  that  an  even 
hardening,  or  rather,  an  even  drying,  of  the  mass  may  take 
place,  so  as  not  to  produce  a  hardened  outer  rim  when  the  inner 
substance  is  yet  soft,  i.  e.,  contains  more  H.  The  H,  which  is 
becoming  rarefied  by  the  increase  of  heat,  has  not  the  power  to 
force  itself  through  the  hardened  parts  ;  it,  however,  possesses  a 
considerable  power  of  expansion,  which  increases  by  the  constant 
application  of  heat ;  it  therefore  forms  a  cavity  for  itself  in  which 
the  yet  unhardened  rubber  deposits  its  H  as  long  as  it  escapes 
from  the  rubber,  and  until  it  is  free  from  it  and  becomes  hard. 
This  is  a  supposition  which  becomes  more  clear  by  future  state- 
ments. 

"  Accordingly,    in    order    to    prevent    porosity,    nothing    else 
is    necessary    than    to    heat    it     in   such    a    manner    that    the 


RUBBER  OR  VULCANITE  BASE.  533 

heat  is  equally  distributed.  This  result  is  obtained  by  observ- 
ing :— 

"  I.  That  the  heat  is  equal  on  all  surfaces,  and 

"  2.  That  the  heat  be  gradually  raised  and  continued,  accord- 
ing to  the  thickness  of  the  plate. 

"  In  making  plates  o{  considerable  thickness,  experience 
taught  us  to  observe  the  above  rules,  or  the  strength  would  be 
lessened. 

"  It  was  mentioned  before  that  steam,  like  oil  or  paraffin, 
serves  simply  to  conxeythe  heat.  It  furthermore  possesses  two 
other  properties  which  make  it  more  valuable  than  the  other 
substances  :  i.  Its  well  known  property  of  conducting  heat.  2. 
Its  elasticity.  Inconsequence  of  its  conductibility, it  distributes 
the  heat  evenly  ;  and  in  consequence  of  its  elasticity,  it  prevents 
an  uneven  rise  of  its  temperature,  while  oil,  e.^.,  will  follow  any 
change  in  the  temperature  that  may  be  caused  by  the  applied 
heat.  Consequently,  steam  serves  as  a  reservoir  of  heat,  as  a 
balance-wheel  serves  as  a  reservoir  of  power ;  as  the  latter  dis- 
tributes the  force,  so  does  steam  distribute  evenly  the  over- 
abundance of  heat  from  one  point  where  the  flame  is  larger,  or 
for  a  moment  when  the  heat  is  greater  it  is  equalized  over  the 
surface  and  over  several  minutes  of  time.  Therefore,  if  the  rub- 
ber exposed  to  it  is  not  too  thick,  so  that  its  influence  can  reach 
through  the  whole  mass  of  the  poorly  conducting  rubber,  one 
may  be  certain  that  by  the  use  of  steam  the  heat  exerts  its  influ- 
ence evenly  and  the  temperature  also  rises  equally.  There  need 
be  no  fear,  therefore,  that  one  place  will  be  harder  than  another, 
as  is  often  the  case  with  oil ;  also  the  temperature  maybe  raised 
higher,  and,  consequently,  less  time  required  for  the  process,  and 
no  fear  entertained  on  account  of  porosity. 

"  Another  property  of  steam  may  here  be  considered  which 
exerts  a  still  greater  influence  than  either  its  conductibility  or 
elasticity,  and  which  also  hastens  the  process  I  have  illustrated, 
chemical  affinity  ;  viz. :  the  magnetic — that  is,  the  power  of  sub- 
stances to  form  certain  compounds. 

"  The  steam  acts  like  a  magnet  upon  the  sulphureted  hy- 
drogen, dissolving  this  gas  with  a  great  deal  of  alacrity,  forming  a 
solution  of  sulphuretted  hydrogen. 


534 


MECHANICAL    DENTISTRY. 


"  It  is  true  that  the  property  of  steam  is  contradictory  to  the 
formation  of  II2S  within  the  rubber.  The  hardening,  in  my 
opinion,  is  nothing  more  than  dry  distillation,  and  this  is  nothing 
more  than  '  slow  burning  by  the  exclusion  of  air.'  This  takes 
place  more  rapidly  the  better  the  provisions  are  for  carrying 
away  the  products  of  combustion,  such  as  carbonic  acid,  oxid 
of  carbon,  etc.,  and  the  same  is  the  case  in  any  chemical  change. 
"What  the  chimney  is  in  the  burning  of  wood,  the  steam  is  in 
vulcanization.  In  the  latter,  the  product — that  is,  theH2S — is 
readily  taken  up  by  the  steam,  thus  furnishing  the  opportunity 
for  more  to  be  formed,  and  permitting  the  rubber  to  harden 
quickly.  This  is  the  main  reason  why  we  can  vulcanize  faster 
when  using  steam,  than  either  oil  or  sand. 

"  The  other  properties  of  steam  permit  of  raising  the  tempera- 
ture rapidly,  and  by  absorbing  the  gas  which  is  formed,  serve  as 
a  proof  of  the  foregoing  assertion,  that  the  hardening  of  rubber 
takes  place  by  the  escape  of  one  equivalent  of  H.2,  and  that 
porosity  is  caused  by  hindering  the  escape  of  this  gas." 

The  Time  and  Temperature  Necessary. — As  solid  fuel  is 
no  longer  employed  in  vulcanizing,  any  description  of  the  appa- 
ratus especially  adapted  to  this  mode  of  producing  heat  is  deemed 

unnecessary.  They  have  been  en- 
tirely superseded  by  others  of  im- 
proved form  and  construction 
adapted  to  the  use  of  either  gas, 
alcohol,  or  coal-oil  and  its  products, 
for  heating  purposes.  After  the 
lamp  or  burner  has  been  lighted,  it 
should  be  so  regulated  as  to  require 
a  half  Jwiir  to  raise  the  temperature 
to  the  vide a)ii7Jng  point,  320°  F.,  or 
120  lbs.  pressure  by  steam  gauge. 
This,  of  course,  is  for  ordinary 
work  ;  where  for  any  reason  the  rubber  is  unusually  thick  the 
time  for  running  it  up  to  the  vulcanizing  point  should  be  ex- 
tended to  one  hour  or  more,  according  to  the  thickness  of  the 
mass,  as  tJie  heat,  if  run  up  too  rapieily,  will  cause  the  rubber  to 
become  spongy  or  porous. 


RUBBER    OR    VULCANITE    BASE. 


535 


The  Hayes  Vulcanizers. — Fig.  530  represents  one  of  Dr. 
Hayes'  Single  Flask  Iron-clad  Ovens,  convenient  and  compact 
in  form,  and  capable,  it  is  claimed,  of  vulcanizing  in  forty 
minutes  at  a  temperature  of  320°,  with  one  ounce  of  alcohol. 
Instruments  of  similar  construction  are  produced  by  the  same 


Fir..  531. 


manufacturer  with  a  larger  boiler  capacity  for  from  one  to  three 
cases,  Fig.  531. 

The  iron-clad  improvement  in  these  machines  is  designed  as 
a  protection  from  the  dangers  of  explosion  consequent  upon  a 
gradual  thinning  of  the  copper  boiler  from  corrosion,  a  safeguard 
of  great  practical  value  and  concern  to  those  who  are  continually 
exposed  to  the  perils  of  such  an  accident.     The  shell  is  made  of 


536  MECHANICAL    DENTISTRY. 

malleable  iron,  one-eighth  of  an  inch  thick,  strong  enough  to 
resist  many  times  the  strain  required,  and  can  never  be  exposed 
to  deterioration.  The  copper  lining  is  made  the  same  thickness 
as  the  copper  boilers  now  in  use,  and  the  machine  may  be  used 
with  perfect  safety,  even  when  the  copper  has  become  as  thin  as 
paper  ;  and  then,  when  an  opening  has  been  fairly  eaten  through, 
steam  will  escape  from  between  it  and  the  iron  shell,  below  the 
packing  joint,  giving  timely  notice  that  a  new  lining  is  required, 
which  can  be  inserted  at  moderate  expense,  and  render  the  vessel 
good,  and  safe  as  new. 

A  peculiar  and  important  feature  of  these  vulcanizers  is  in 
placing  the  thermometer  bulb  within  a  mercury  bath,  outside  the 
steam-chamber,  relieving  it  entirely  from  the  danger  of  being 
crushed  or  checked  by  the  pressure  of  steam,  as  is  liable  to 
happen  when  it  is  exposed  to  the  steam  itself,  necessitating  its 
frequent  replacement. 

In  the  accompanying  illustration  the  Time  and  Gas  Regulator 
is  also  shown.  This  regulator  (the  Coolidge-Levvis)  is  without 
doubt  the  most  convenient  and  perfect  in  its  action  and  adjust- 
ment of  any  yet  constructed. 

The  pointer  is  so  constructed  that  it  acts  as  a  stop  by  coming 
in  contact  with  the  inlet  tube.  This  stop  prevents  the  regulator 
from  being  set  either  by  design  or  accident  to  maintain  a  higher 
temperature  than  the  highest  graduation  on  the  base,  and  en- 
dangering the  safety  of  the  vulcanizer.  It  also  requires  no 
special  adjustment  after  leaving  the  factory. 

To  vulcanize  at  any  of  the  degrees  of  temperature  marked  on 
the  graduated  base,  all  that  is  required  is  to  turn  the  milled 
hand-plate  till  the  pointer  is  over  the  degree  desired.  This  can 
be  done  either  before  or  after  lighting  the  gas  under  the  vulcan- 
izer. 

It  should  not  be  forgotten  when  vulcanizing  at  a  low  heat  to 
extend  the  time  of  vulcanization. 

Better  results  are  obtained  by  running  the  vulcanizer  from  an 
hour  and  a  half  to  two  hours — exclusive  of  the  time  of  heating 
up — at  a  low  heat. 

This  Graduated  Gas  Regulator  is  provided  with  a  by-pass 
screw  adjustable  to  different  pressures  of  gas.     The  adjustment, 


RUBBER    OR    VULCANITE    BASE. 


537 


as  it  leaves  the  factory,  is  for  coal  gas — low  pressure.  If  the 
regulator  is  to  be  used  with  natural  gas,  at  a  high  pressure,  too 
much  gas  will  be  passed  after  the  proper  temperature  has  been 
reached.  A  re-adjustment  of  the  by-pass  will  then  be  required. 
This  is  accomplished  by  turning  the  small  screw  on  the  side  ot 
the  gas  chamber  till  the  flame  maintains  the  heat  at  the  proper 
temperature.  Fuller  instructions  accompany  these  regulators 
when  sold  to  the  profession. 

The    Whitney   Vulcanizer. — A    not    less    convenient,   safe, 


Fig.  532. 


and  reliable  vulcanizer  is  that  known  as  Dr.  Whitney's,  repre- 
sented in  Fig.  532,  having  a  steam -chamber  capacity  for  from 
one  to  three  flasks. 

The  Snowden  &  Cowman  Vulcanizer  is  illustrated  in  Fig. 
533.  It  is  an  approved  apparatus  of  more  recent  introduction, 
resembling  somewhat  the  Hayes  vulcanizer  in  general  construc- 
tion, differing  somewhat  in  the  method  of  fastening  the  cover, 
which,  in  the  latter,  is  placed  upon  the  packing  joint  and 
secured  by  a  screw  collar  which  screws  over  the  edge  of  the 
pot,  three  set-screws   which  bear  upon  the  cover,  to  make  the 


538 


MECHANICAL    DENTISTRV. 


joint  Steam  tight,  while  in  the  Snowden  &  Cowman  apparatus 
the  collar  has  lugs  upon  its  interior  engaging  with  others  upon 
the  pot,  thus  dispensing  with  the  screw  thread. 

The  Mann  Vulcanizer,  rigged  for  gas  or  alcohol,  is  shown 


in  Figs.  534  and  535.  The  same  apparatus  has  stove  attachment 
for  the  use  of  kerosene,  and  admits  of  the  use  of  thermometer 
or  steam  gauee. 


RUBBER    OR    VULCANITE    BASE. 


539 


The  facility  with  which  this  vulcanizer  may  be  operated  is 
one  of  its  distinctive  features.  The  lid,  instead  of  being  screwed 
on  to  the  boiler,  is  fitted  neatly,  and  rests  on  a  shoulder  formed 
on  the  casting,  and  is  secured  by  a  heavy  steel  clamping-bar 
and  screw-bolt.  One  end  of  the  bar  is  hinged  to  the  side 
of  the  boiler,  the  outer  end  being  slotted  to  receive  the  screw- 
bolt,  which  is  hinged  to  the  other  side  of  the  boiler.  Rubber 
packing  between  the  lid  and  the  shoulder  on  which  it  rests 
makes  the  joint  steam-tight.     The  lid  is  removed  by  unscrew- 


FiG.  534. 


ing  the  nut  of  the  screw-bolt  a  turn  or  two,  when  the  bolt  drops 
out  of  the  slot  and  the  bar  is  turned  back,  leaving  the  lid  free  to 
be  removed.  This  method,  while  it  gives  as  perfect  a  fastening 
as  the  usual  plan,  affords  very  much  greater  facility  for  opening 
and  closing  the  boiler.  Should  it  stick,  by  reason  of  the  pack- 
ing becoming  chilled  (a  common  occurrence  with  all  vulcan- 
izers),  it  is  pried  off  with  very  much  less  trouble  than  is 
required  when  the  top  screws  on. 

Another  advantage  is  the  bail,  a  simple  but    heretofore  un- 


540 


MECHANICAL    DENTISTRY. 


thought-of  device,  which  greatly  facihtates  the  handhng  of 
the  vulcanizer,  especially  when  hot.  Thus  the  boiler  can 
be  opened  for  the  removal  of  one  case  and  the  placing 
of    another.     The     nut    of   the    clamping-bolt    is    loosened    a 

Fig.  536. 


little  at  a  time,  allowing  the  steam  to  escape  gradually  until  the 
bolt  is  released,  when  the  bar  can  be  thrown  back  and  the  top 
of  the  boiler  raised.  The  bail  is  also  useful  in  removing  the 
boiler  from  the  jacket,  in  tightening  or  loosening  the  screw-bolt 


RUBBER    OR    VULCANITE    BASE. 


541 


when  closing  or  opening  the  boiler,  and  at  all   times  when   the 
boiler  is  to  be  lifted.     When  not  in  use  it  is  readily  removed. 

The  Hood  &  Reynolds  Vulcanizer,  the  several  parts  of 
which,  ill  situ  and  detached,  are  exhibited  in  Fig.  536,  involves 
a  principle  of  closure  similar   to  the  one   last  mentioned.      It  is 


Fig.  537. 


made  from  a  seamless  copper  pot  which  the  inventors  claim  is 
four  gauges  thicker  than  any  in  the  market. 

Place  the  cover  on  the  boiler  with  the  pins  corresponding  with 
the  holes  in  the  cover  ;  now  shut  down  the  lever  and  screw  down 
the  cover.     To  replace  safety  disk,  unscrew  nut  on  top  of  the 


542  MECHANICAL    DENTISTRY. 

steam  cock.  Should  the  disk  burst  at  any  time  while  vulcaniz- 
ing, turn  the  valve  in,  which  shuts  the  steam  off  To  blow  off 
steam,  loosen  screw  on  cover,  and  let  steam  out  under  it. 

The  Boston  Vulcanizer. — This  vulcanizer,  manufactured  by 
the  Boston  Dental  Manufacturing  Co.,  is  made  of  the  best 
bronze,  so-called  "  gun-metal,"  and  is  tested  at  one  thousand 
pounds  hydraulic  pressure.  It  will  hold  three  flasks  of  any 
kind  with  Donham  spring,  and  allow  plenty  of  room  for  hand- 
ling. The  packing  is  molded  instead  of  being  cut  in  strips, 
and  will  last  for  years  without  being  renewed.  The  cover  can 
be  screwed  steam  tight  without  the  use  of  a  wrench,  the  same 
being  necessary  only  to  open  after  being  heated.  The  small 
quantity  of  water  used  (one  gill)  produces  vulcanizing  by  steam, 
instead  of  water,  thus  giving  better  results.  The  bed-plate 
jacket,  which  is  screwed  to  the  bench,  allows  an  easy  and 
ready  method  of  handling.     It  is  illustrated  in  Fig.  537. 

The  "  New  Mode  Heater,"  designed  alike  for  vulcanizing  and 
molding  celluloid,  will  be  described  and  illustrated  under  the 
head  of  "Celluloid  Base,"  inasmuch  as  it  is  more  commonly  em- 
ployed for  the  latter  purpose,  and  for  which  it  enjoys  a  deservedly 
high  reputation. 

The  Seabury  Steam  Vulcanizer. — Fig.  538  represents  the 
general  body  and  Fig.  539  a  transverse  vertical  section  of  Dr. 
Frederick  W.  Seabury's  Superheated  Steam  Vulcanizer  and  Cel- 
luloid Press  combined  in  one  apparatus,  which,  it  is  claimed,  will 
enable  the  intelligent  dentist  who  does  not  wish  to  be  restricted 
to  the  use  of  one  plastic  material  to  accomplish  results  never 
before  attained.  Rubber  and  celluloid  can  be  manufactured  with 
this  apparatus  in  less  than  half  the  time  usually  required, 
and  a  perfect  product  assured  every  time.  Both  rubber  and  cel- 
luloid come  out  of  the  vulcanizer  finished. 

Cases  may  be  removed  from  the  oven  and  others  inserted  at 
any  time  during  the  process  of  vulcanization  with  a  delay  not 
to  exceed  five  minutes,  which  is  a  great  saving  of  time,  espe- 
cially with  repair  work.     The  apparatus  is  thus  described : — 

"In  the  accompanying  drawing.  Fig.  539,  No.  i  illustrates  a 
transverse  vertical  section  of  the  vulcanizer  with  dental  flasks  in 
position. 


RUBBER    OR    VULCANITE    BASE. 
Fig.  538. 


543 


"  In  the  said  drawing,  A  designates  the  hollow  body  of  the 
ailcanizer,  which  is  supported  on  the  legs,  a.     Within  this  body 


544 


MECHANICAL    DENTISTRY. 


is  placed  the  boiler,  B,  which  is  formed  with  the  central  inverted 
truncated  conical  flue,  C.  The  boiler  and  flue  are  supported  by 
the  tubes,  d,  which  are  connected  at  one  end  to  the  top  of  the 
boiler  and  at  the  other  end  to  the  chamber,  d''. 


Fig.  539. 


No.  2 


"  D  designates  the  oven,  the  lower  end  or  base  of  which  ex- 
tends somewhat  downward  into  the  upper  end  of  the  flue,  C. 

"  The  upper  end  of  the  oven  is  formed  with  lateral  flanges 
d^,  which  rest  upon  the  top  of  the  case  or  body.  A,  and  thus 


RUBBER    OR    VULCANITE    BASE.  545 

support  the   oven   in   position,  and   also   form   the   top   of  the 
vulcanizer. 

"  E  designates  the  pressure  cover  of  the  oven,  which  is  secured 
in  position  by  bolts,  as  shown. 

'' e e  designate  presser-screws,  which  work  through  square 
threaded  sockets  in  the  cover  and  press  upon  the  flask,  F,  in  the 
oven  supported  upon  the  disk,  ;//. 

"  E  ^  designates  two  lids,  which  are  pivoted  upon  the  cover  in 
such  manner  as  to  be  readily  removed,  and  by  uncovering  aper- 
tures in  the  cover  permit  visual  access  to  the  interior  of  the  oven. 

"  G  designates  a  valve,  which  is  seated  in  the  flange,  ^\  of  the 
oven  so  as  to  close  the  channel,  d'-,  leading  from  the  pipe,  d,  to 
the  interior  of  the  oven. 

"  H  designates  a  spout.  The  outer  end  of  it  is  tightly  closed 
by  the  cap,  h,  which  leads  into  the  tube,  I,  entering  the  chamber, 
d'\  from  above.  The  purpose  of  this  spout  is  to  convey  water  to 
the  boiler,  B. 

"  i  designates  a  pop  safety-valve,  which  is  seated  on  the  upper 
end  of  the  tube,  I.  J  designates  a  steam-gauge  connected  by  the 
siphon  cock,  J,  to  the  chamber,  d'"^,  into  which  the  tube,  d,  opens. 

"  K  designates  a  test- cock  communicating  with  the  chamber, 
d^,  and  b  designates  a  similar  cock,  communicating  with  the 
boiler,  B,  on  the  water  level. 

"  In  using  this  vulcanizer  a  gas  or  gasoline  burner  is  set  be- 
neath the  boiler,  B,  and  the  valve,  G,  is  closed  ;  but  the  test- cock, 
K,  is  not  closed  until  the  escaping  steam  shows  that  all  of  the  air 
is  out  of  the  boiler.  The  heat  from  the  burner  will  ascend 
through  the  flue,  C,  and  will  act  directly  upon  the  bottom  and 
sides  of  the  oven,  thus  heating  the  oven  and  water  which  has 
been  previously  placed  in  the  boiler,  at  the  same  time  or  sepa- 
rately. 

"  Fig.  2  illustrates  a  vertical  section  of  the  solid  cover  which 
is  used  at  all  times,  except  when  closing  the  flask,  and  occupies 
the  same  position  on  the  vulcanizer  as  the  presser-cover,  E.  It 
is  provided  with  a  very  sensitive  thermometer,  immersed  in  a 
mercury  bath,  d,  which  projects  into  the  oven,  D,  and  a  test-cock, 
7',  used  to  let  the  air  out  of  the  oven  before  vulcanizing  and  to 
blow  the  steam  out  through  after  vulcanizing. 
35 


546  MECHANICAL    DENTISTRY. 

"  The  bar-wrench  is  to  be  used  on  the  cover  bolts  only,  and 
must  never  be  used  on  the  presser-screws,  e  e,  for  which  the  T- 
wrench  is  provided. 

''  To  Adjust  the  Vulcanizer  for  Use. — Open  the  test-cocks, 
b  and  k,  remove  the  cap,  h,  pour  clean  water  into  the  spout,  H, 
until  it  escapes  through  the  test-cock,  b.  Replace  the  cap,  //, 
turn  it  to  place  with  the  fingers.  If  it  should  leak  when  the 
steam  is  up,  tighten  it  very  gently  with  the  T-wrench.  Close 
the  test-cock,  b,  after  the  excess  of  water  has  run  out. 

"  Place  the  s^as  or  grasoline  burner  so  it  will  heat  the  oven  and 
boiler  at  the  same  time  when  you  wish  to  vulcanize.  One  bur- 
ner may  be  used  under  the  boiler,  the  other  in  the  flue. 

"  For  celluloid,  place  the  burner  in  the  center  of  the  flue, 
elevate  it,  if  necessary,  on  a  box,  that  as  little  steam  as  possible 
may  be  generated  in  the  boiler.  The  pressure  of  coal  gas  varies 
in  different  places  ;  a  little  judgment  is  necessary  to  vary  these  in- 
structions to  suit  each  place.  It  takes  less  than  thirty  minutes  with 
cold  water,  and  less  time  still  with  hot  water,  to  get  120  pounds 
pressure  of  steam.  When  steam  is  up,  it  requires  very  little  heat 
to  keep  it. 

"  The  water  should  be  renewed  every  morning  the  first  thing, 
or  some  time  the  pressure  will  decrease  apparently  without  any 
cause. 

"  Close  the  test-cock,  k,  when  steam  escapes,  and  not  until 
then.  When  the  pressure  reaches  120  pounds  the  pop-valve,  i, 
will  blow,  at  first  too  freely ;  a  gentle  tap  on  top  will  seat  it. 

"  The  valve,  G,  is  packed  with  asbestos ;  a  piece  is  sent  with 
each  machine.  If  the  packing  leaks,  tighten  the  screw  gently. 
When  the  screw  reaches  its  seat,  turn  it  back,  oil  some  asbestos, 
make  two  or  three  turns  around  the  stem,  and  press  it  in  so  that 
the  screw  will  catch.  Turn  this  screw  very  gently,  or  you  will 
bulge  the  barrel.  The  asbestos  will  wear  one  year,  to  my 
knowledge,  and  look  as  fresh  as  new. 

"  When  operating  the  machine  in  vulcanizing,  the  valve,  G,  and 
the  test-cock,  v,  should  be  opened  gradually  and  slowly.  By 
opening  the  valve,  G,  quickly,  the  rushing  steam  will  siphon  water 
from  the  boiler  into  the  oven.  When  vulcanizing,  there  is  115 
pounds  pressure  inside  the  flask  as  well  as  in  the  oven.     By  in- 


RUBBER    OR    VULCANITE    BASE.  547 

stantly  turning  the  test-cock,  v,  wide  open,  the  pressure  is  removed 
from  the  outside  of  the  flask,  and  the  pressure  then  comes  from 
the  inside,  which  it  is  least  able  to  withstand. 

"  On  the  inside  of  the  oven,  midway  from  top  to  bottom,  are 
four  brackets  to  suspend  the  disk,  M.  On  the  bottom  side  of 
this  disk  are  two  small  projections  which  fit  between  the 
brackets  under  the  steam-gauge,  and  thereby  keep  the  disk 
stationary.  On  the  upper  side  of  the  disk,  above  the  small  pro- 
jections, are  two  large  projections  placed  so  as  to  receive  the 
square  projection  on  the  broad  side  of  nowel ;  it  holds  the  flask 
when  under  pressure  directly  beneath  the  three  presser-screws. 
When  it  is  in  the  right  position,  the  lock-pins  of  the  flask  will 
come  directly  under  the  holes,  EE,  in  the  presser-cover,  through 
which  the  pins  are  driven  home  in  locking.  On  the  bottom  side 
of  this  disk,  in  the  center,  is  a  groove  cut  to  receive  the  ridge 
of  the  flask  placed  on  the  bottom  to  keep  warm  while  molding 
celluloid  or  rubber  in  the  other  flask.  When  drying  out  or 
heating  up  the  investments,  the  disk  is  left  out  of  the  oven. 
When  heating  up  celluloid  investments,  put  the  flask  in  bottom 
side,  or  nowel,  up,  because,  there  being  more  plaster  in  the  cope, 
it  requires  more  heat  than  the  nowel  with  the  metal  die.  In 
rubber,  rubber  and  celluloid,  and  gold  and  celluloid,  put  the  flask 
in  bottom  side  down.  The  flask  being  in  position,  put  on  the 
presser-cover — the  small  curve  in  the  circumference  fits  the  siphon 
bulb, — with  the  bar-wrench  tighten  the  cover  bolts  by  giving  each 
a  half-turn  in  succession  until  the  cover  is  seated,  then  with  the 
T-wrench  turn  the  presser-screws  gently.  The  bar-wrench  must 
never  be  used  on  the  presser-screws.  The  presser-cover  is  only 
used  when  molding.  For  drying  out,  heating  up,  and  \v\c?l\'\\z- 
ing,  use  the  .w//^  rtiz'^r.  Place  the  solid  cover  in  position,  first 
see  that  the  ground  joint  is  perfectly  clean,  tighten  the  bolts  by 
giving  each  a  half-turn  successively;  tlic  bolts  vutst  go  down 
evoily  or  the  Joint  zvill  leak.  Coat  the  ground  joint  occasionally 
with  bar-soap. 

"  Before  putting  the  flask  into  the  oven  to  mold,  always  insert 
the  lock-pins  into  the  holes  in  the  cope,  then,  when  the  flask  is 
closed,  they  can  be  easily  driven  down." 

Evans'  New  Vulcanizer  and  Celluloid  Apparatus. — Figs. 


548 


MECHANICAL    DENTISTRY. 


540  and  541  represent  Dr.  W.  W.  Evans'  New  Vulcanizer  and 
Celluloid  Apparatus  combined,  which  is  claimed  to  possess 
superior  qualities  for  vulcanizing  rubber  and  molding  celluloid 
and  zylonite. 

Fig.  540  shows  front  elevation  with  top  attached  and  tools 
needed  in  the  working  of  this  apparatus,  which  is  thus  de- 
scribed : — 

"Fig.  541  illustrates  a  transverse  vertical  section  with  one 
flask  in  position.     A  is  a  light  casing,  B  the  boiler,  composed  of 


Fig.  540. 


Fig.  541. 


-C-     -^r^       I  llHilll  IHIIIIIIIIHftJ 


two  separate  cups,  /;-  d,  united  concentrically  by  screws,  d\  to 
form  a  water  and  steam  space.  The  bottom  of  the  boiler,  A,  is 
partly  concave,  to  facilitate  ebullition  and  keep  the  steam  in  a 
state  of  agitation.  D  illustrates  the  oven  composed  of  the 
inner  cups,  d,  having  a  cover.  C  is  an  inlet  for  steam,  d, 
through  the  cup,  d,  from  the  boiler,  and  an  exit  for  steam 
through  the  cover,  d'^,  both  openings  being  controlled  by  valves, 
(P  and  d'\  E  E  represent  the  bolts  with  spherical  heads  at  c,  the 
point  of  contact  with  the  cover,  C,  which  has  a  corresponding 


RUBBER    OR    VULCANITE    BASE.  549 

socket  to  receive  it,  thus  making  a  steam-tight  joint.  The  top 
of  the  head,  c'~,  is  made  to  fit  the  T-wrench,  that  also  fits  the 
different  valves.  To  gain  more  pressure  than  is  usually 
required,  an  additional  sexangular  portion,  c^,  has  been  made, 
whereby  any  amount  of  pressure  can  be  exerted.  The  lower 
portion  of  the  bolt  is  threaded  for  one-half  its  distance,  and 
screws  into  or  through  the  platen,  F,  which  is  drawn  toward  the 
top  by  turning  the  bolts  to  the  right,  thus  closing  the  flasks,  G, 
with  facility  and  without  any  strain  upon  the  boiler.  /  is  the 
thermometer,  on  either  side  of  which  are  valves,  one  connecting 
the  boiler  with  the  oven  ;  the  other  a  conical  safety-valve,  so 
arranged  that  the  steam  in  the  boiler  can  never  go  higher  than 
the  point  at  which  the  safety-valve  is  set.  I  is  a  handle  to 
remove  the  top.  Tw^o  large  flasks  may  be  used  at  a  time,  and 
it  is  claimed  that  it  will  readily  stand  from  250  to  300  pounds 
pressure.  It  is  also  claimed  that  rubber  vulcanized  in  this 
apparatus  is  much  more  elastic,  denser,  and  tougher,  and  retains 
its  color  better  than  by  other  processes,  and  that  it  will  not 
shrink  from  the  teeth,  and  can  be  vulcanized  in  thicker  masses 
without  becoming  porous.  For  celluloid  and  zylonite,  better 
results,  shorter  time  of  molding  (one  hour  and  a  half),  and  no 
lost  steam  from  the  boiler,  are  claimed." 

Whatever  form  of  water-bath  vulcanizing  apparatus  is  used, 
the  flasks  are  introduced,  and  sufficient  water  poured  in  to  cover 
them.  If  the  flasks  are  hot  when  placed  in  the  boiler,  water  of 
nearly  the  same  temperature  should  be  added  to  avoid  fractur- 
ing the  teeth  by  too  sudden  cooling.  Before  screwing  on  the 
cap,  the  rubber  packing  should  be  dusted  with  whiting  or 
pulverized  soapstone,  to  prevent  adhesion.  As  it  is  very 
important  to  secure  a  rteam-tight  joint,  the  packing  should  be 
uniform,  firm,  and  securely  fixed.  The  webbed  rubber  is  the 
best  for  the  purpose.  In  arranging  a  new  packing,  cleanse  well 
the  groove  in  the  boiler  which  receives  the  rim  of  the  cap,  and 
fit  the  packing  accurately.  Before  screwing  on  the  top,  dust  the 
surface  of  the  packing  as  before  recommended,  and  as  the  heat 
rises  tighten  the  screw  from  time  to  time  until  the  rubber  no 
longer  yields.  If  the  latter  precaution  is  not  observed,  the 
packing   is   either   liable    to  blow  out   or  the    joint   may  leak. 


550 


MECHANICAL    DENTISTRY. 


To  insure  uniform  results,  it  is  necessary  that  there  should  be 
absolutely  no  leakage. 

When  the  flasks  are  properly  secured  within  the  steam- 
chamber,  heat  is  applied  and  continued  until  the  requisite 
induration  of  the  gum  is  affected.  The  time  and  degrees  of 
heat  necessary  to  effect  this  result  differ  somewhat  with  the 
rubber  compounds  and  kind  of  vulcanizer  employed.  The  heat 
should  be  raised  gradually  until  the  thermometer  indicates  the 
proper  vulcanizing  temperature,  when  the  flame  should  be  low- 
ered, and  the  heat  maintained  at  this  point  until  vulcanization  is 
completed.  In  all  cases  it  is  best  to  raise  the  heat  slowly  until 
it  reaches  320°,  which  temperature  should  not  be  attained  in 
less  than  from  one-half  to  three-quarters  of  an  hour.  Where 
there  is  any  considerable  or  unusual  body  of  rubber,  the  time 
taken  to  raise  the  heat  to  that  point  should  be  extended  to  one 
hour  or  longer,  for  if  the  mass  is  heated  too  rapidly,  porosity  or 
sponginess  of  the  thicker  portions  of  the  rubber  will  almost 
certainly  ensue.  This  result  would  seem  to  be  due  to  the 
energetic  evolution  of  sulphureted  hydrogen  gas  under  a  quick 
heat,  the  proper  elimination  of  which  is  checked,  and  the  gas 
confined  within  the  body  of  the  mass  by  a  too  rapid  surface- 
vulcanization  of  the  rubber.  The  evolution  of  this  gas  is  demon- 
strated by  Prof.  Wildman  in  the  following  experiment : — 

"To  ascertain  if  sulphureted  hydrogen  is  given  off  during 
vulcanization,  a  bulb  was  blown  at  the  end  of  a  glass  tube ;  this 
was  filled  with  red  rubber  ;  the  tube  was  then  drawn  out  very 
small  from  immediately  above  the  bulb,  and  curved  so  that  the 
small  part  when  the  bulb  was  in  the  paraffin  bath  could  be 
inserted  into  a  vessel  beside  it. 

"  The  bulb  was  then  placed  in  a  paraffin  bath,  and  the 
curved  end  of  the  tube  inserted  in  a  vessel  containing  a  solution 
of  acetate  of  lead.  The  heat  was  raised  to  320°  F.,  and  retained 
at  that  point  for  one  hour  and  a  quarter. 

"  The  mean  result  of  several  experiments  conducted  in  this 
manner  was,  that  during  the  first  thirty  or  forty  minutes  after 
the  heat  had  a.ttained  to  320°,  bubbles  of  sulphureted  hydrogen 
came  over  at  short  intervals,  and  at  the  expiration  of  this  time 
it  was  evolved  in  a  continuous  stream,  which  continued  for  a 


RUBBER  OR  VULCANITE  BASE.  55  I 

few  minutes,  causing  a  copious  precipitate  of  sulphid  of  lead. 
After  this,  until  the  expiration  of  the  hour  and  a  quarter,  the 
gas  was  only  given  off  sparingly  at  intervals.  This  experiment 
gives  us  ocular  demonstration  that  this  gas  is  evolved  during 
vulcanization,  and  in  large  quantities,  and  conclusively  shows 
that  in  thick  pieces  especially  the  heat  should  be  slowly  raised, 
and  the  rubber  should  be  under  strong  pressure  to  insure  a 
successful  result." 

When  the  American  Hard  Rubber  Company's  red  rubber  is 
used,  the  heat  should  be  maintained  at  320°  for  about  one  hour 
and  ten  or  twenty  minutes.  Vulcanization  may  be  effected  at  a 
lower  heat,  but  the  time  must  be  proportionally  extended  ;  or  a 
higher  heat  being  employed,  a  less  time  will  be  required  to  vul- 
canize. Care  should  be  taken,  however,  not  to  overheat,  as  the 
rubber  is  thereby  rendered  dark  and  brittle,  and  the  important 
property  of  elasticity  impaired.  The  time  and  degrees  of  heat 
mentioned,  therefore,  may  be  regarded  as  the  safest,  and  as  yield- 
ing the  best  results,  though  with  other  rubber  compounds,  and 
the  use  of  modified  forms  of  vulcanizers.  corresponding  differ- 
ences in  time  and  temperature  may  be  required,  and  which  can 
only  be  accurately  determined  by  vulcanizing  test-pieces  of 
rubber. 

In  this  connection  the  reader's  attention  is  called  to  some 
practical  observations  on  the  subject  of  steam  pressure  in  vul- 
canizing, and  the  reliability  of  thermometers  as  indicators  of 
heat,  and  which  acquire  additional  interest  if  it  be  true,  as  alleged, 
that  many  of  the  vulcanizers  in  use  by  dentists  are  insecure  by 
reason  of  inherent  defects  of  construction  or  faultiness  in  the 
modes  of  indicating  the  elastic  force  of  steam.  In  commenting 
on  this  subject  the  late  Prof  Wildman  observes  : — * 

"As  high  steam  is  used  in  vulcanizing,  it  is  important  that  the 
operator  should  be  conversant  with  the  nature  of  the  agent 
which  he  employs  to  accomplish  this  end.  It  is  perfectly  safe  ; 
but  the  following  will  show  him  that  it  must  be  used  with  dis- 
cretion and  judgment.  Numerous  experiments  have  been  made 
by  scientific  men  to  ascertain  the  elastic  force  of  steam  at  differ- 

*"  Instructions  in  Vulcanite,"  p.  26. 


552  MECHANICAL    DENTISTRY. 

ent  temperatures.  The  results  of  their  investigations  are  not 
uniform,  although  they  all  agree  in  showing  the  immense  force 
exerted  by  this  agent  at  high  temperatures.  Haswell's  tables  are 
looked  upon  as  good  authority.  The  results  of  the  investiga- 
tions of  the  Franklin  Institute  Committee,  in  the  higher  degrees, 
give  a  greater  elastic  force  than  the  table  below  quoted.  I  shall, 
however,  quote  the  results  of  the  experiments  of  the  commission 
of  the  French  Academy,  appointed  by  the  French  government 
to  investigate  this  subject,  for  the  reasons  that,  from  the  manner 
in  which  they  were  conducted,  they  are  probably  as  reliable  as 
any,  and  that  they  are  extended  to  a  more  elevated  temperature 
than  the  others. 


Elasticity  of  steam, 
taking  atmospheric 
pressure  as  unity. 

Temperature  F. 

Pressure,  per  square 
inch,  pounds. 

I 

212° 

14.7 

^y^ 

233.96° 

22.05 

2 

250.52° 

29.4 

^% 

263.84° 

36.75 

3 

275.18° 

44.1 

7>%    • 

285.08° 

51.45 

4 

293.72° 

58.8 

A'A 

300.28° 

66.15 

5 

307.05° 

73-5 

VA 

314-24° 

80.S5 

6 

320.36° 

88.2 

6K 

326.26° 

95-55 

7 

331.70° 

102.9 

7^2 

336.86° 

110.S5 

8 

341.78° 

117. 6 

9 

350.78° 

132.3 

lo 

358.88° 

147 

II 

366.85° 

161. 7 

12 

374.00° 

176.4 

13 

380.66° 

191. 1 

14 

386.94° 

205.8 

IS 

392.86° 

220.5 

i6 

398.48° 

235.2 

17 

403.82° 

249.9 

i8 

408.92° 

264.6 

19 

413.78° 

279.3 

20 

418.46° 

294 

I  would  here  call  the  attention  of  those  using  high  steam  to 


RUBBER  OR  VULCANITE  BASE. 


553 


an  important  consideration.  In  raising  steam,  tJie  ratio  of  increase 
of  pressure  or  elastic  force  is  far  greater  than  that  of  the  increase 
of  temperature. 

"By  referring  to  the  above  table,  commencing  at  212°  and 
taking  steps  as  near  50°  as  is  given  in  the  ascending  scale,  we 
find  this  exemplified.     Thus  : —  • 


Increase  of  tempera-  Increase  of  force  per  Giving  a  force  per 
ture.                                                   square  inch.  square  inch. 

From  212°       to  263.84°  =3  51.85°  22.05  fts.  36.75  lbs. 

"      263.8410   314.24°  =  50.40°  44.10  lbs.  80.85  lbs. 

"         314.24    to     366.85°  =  52.61°  80.85  lt)S.  161.85   1^3S. 

"         366.85    to     418.46°  =r  51.61°  132.151115.  294  fts. 


"  This  comparison  shows  clearly  how  rapidly  the  pressure 
increases  at  high  temperatures,  and  warns  the  operator  that  a 
strong  instrument  combined  with  care  and  judgment  in  its  treat- 
ment are  indispensable  to  safety.  Besides  the  rapid  increase  of 
pressure,  it  must  be  borne  in  mind  that  at  high  temperatures, 
copper,  of  which  the  boiler  is  composed,  becomes  weakened,  and 
in  a  measure  loses  its  power  to  resist  this  great  imprisoned  force. 
Copper,  in  passing  from  212°  to  230°  F.,  loses  about  one-tenth 
of  its  strength,  and  at  550  it  has  lost  one-fourth  of  its  tenacity." 

In  a  paper  read  before  the  Massachusetts  Dental  Association, 
January,  1865,  Dr.  A.  Lawrence  affirms  that:  "  Most  vulcanizers 
are  now  made  of  sheet  copper  one-sixteenth  of  an  inch  in  thick- 
ness, and,  agreeably  to  the  foregoing  facts,  have  a  tensile 
strength  of  1875  pounds  ;  and  one  four  inches  in  diameter  will 
not  sustain  a  pressure  of  more  than  150  pounds  per  square  inch, 
or  a  temperature  of  363°. 

"  Let  us  next  ascertain  what  force  of  steam  is  exerted  upon 
the  boiler  within  a  short  range  of  temperatures.  We  find  by  the 
tables  of  Haswell,  King,  and  others,  that  at  320°  the  pressure  is 
85  pounds;  at  324°,  90  pounds;  at  328°,  95  pounds;  and  at 
332°  it  is  100  pounds  per  square  inch.  These  figures  I  have  veri- 
fied by  a  steam-gauge  connected  with  my  own  vulcanizer,  and 
which  I  now  use  in  preference  to  a  thermometer,  as  I  consider  it 
more  convenient,  safer,  and  less  liable  to  accidents. 

"  Practical  engineers  concur  in  the  opinion  that  a  force  of  not 


554  MECHANICAL    DENTISTRY. 

over  one-half  the  sustaining  capacity  of  the  boiler  can  be  safely 
applied." 

Immediately  connected  with  the  process  of  vulcanizing  is  the 
question  of  the  reliability  of  thermometers  as  indicators  of  heat, 
or  steam  pressure.  Dr.  Lawrence,  commenting  on  this  subject, 
says  :  "  Suppose  the  bulb  of  the  thermometer  gets  slightly  frac- 
tured, and,  the  accident  not  being  discovered,  the  vulcanizer  is 
put  to  use,  what  then  ? 

"If  the  damage  is  slight,  the  mercury  may  still  be  made  to 
rise  in  the  tube  at  high  temperatures,  but  will  not  truly  indicate 
the  full  heat  or  force  within.  Some  time  ago  I  had  some  diffi- 
culty in  producing  a  desirable  shade  in  my  vulcanite  work  ;  it 
was  too  dark,  as  is  the  case  when  overheated,  and  I  came  to  the 
conclusion  that  the  gum  had  deteriorated  in  quality.  Other 
samples  of  gum  were  tried,  and  at  varying  lengths  of  time,  yet 
with  the  same  result. 

"  No  defect  could  be  discovered  in  the  thermometer  by  the 
naked  eye,  but  a  microscope  revealed  a  slight  crack  in  the  bulb, 
and  the  mystery  was  solved.  But  what  force  of  steam  was  pro- 
duced during  these  almost  despondent  trials? 

"Although  my  vulcanizer  would  safely  bear  a  pressure  of  lOO 
pounds  per  square  inch,  I  concluded  to  use  a  steam-gauge  for 
the  future,  and  now  feel  a  security  in  its  use  positively  refresh- 
ing." 

The  unreliability  of  thermometers  in  connection  with  vulcan- 
izers  has  been  recognized  by  many  in  the  profession  who  have 
testified  to  their  uncertainty  and  insecurity  as  a  means  of  deter- 
mining with  exactness  at  all  times  the  amount  of  steam  pressure 
employed  in  the  process  of  vulcanizing  at  a  high  heat. 

The  steam-gauge  (Fig.  542)  spoken  of  by  Dr.  L.  seems  very 
perfectly  to  fulfil  the  requirements  of  the  dentist,  and  may  justly 
claim  favorable  consideration  from  the  commendation  bestowed 
upon  it  by  the  distinguished  gentleman  who  has  brought  it  to 
the  notice  of  the  profession.  The  following  is  the  author's  own 
account  of  the  instrument :  "The  gauge  most  suitable  for  the 
purpose  in  question  somewhat  resembles  a  small,  circular  clock, 
is  about  six  inches  in  diameter,  and  marked  to  register  one 
hundred  and  forty  or  one  hundred  and  eighty  pounds  pressure. 


RUBBER    OR    VULCANITE    BASE.  555 

with  pound  dots  near  the  outer  circle  of  the  dial.  A  pointer  in- 
dicates the  force  which  moves  it. 

"  This  size  is  better  than  a  smaller  one,  because  the  spring  in- 
side, not  being  crowded  to  its  utmost  capacity  in  vulcanizing, 
will,  of  course,  retain  its  working  integrity  longer  ;  in  fact,  as 
long  as  any  dentist  now  living  will  be  personally  interested  in 
the  matter.  The  price  of  such  a  gauge,  at  this  time,  is  ;^i8  ; 
and  though,  unquestionably,  more  expensive  ones  can  be  made, 
they  are  no  more  reliable,  the  difference  consisting  in  mere  '  out- 
ward show  and  adorning.'  They  can  be  used  with  all  vulcaniz- 
ers  generating  steam,  connecting  by  means  of  three  or  four  feet, 
or  as  much  more  as  may  be  convenient,  of  small  pipe  having  a 
U-shaped  bend,  or  a  single  coil  near  and  under  the  gauge  to 
receive  the  condensed  steam,  as  water  alone  should  enter  this 
instrument. 

"  The  following  table  exhibits  a  range  of  pressure  sufficient 
for  vulcanizing  purposes,  with  the  temperature  necessary  to  pro- 
duce the  same : — 


Pressure 

Tempera- 

Pressure 

Tempera- 

Pressure 

Tempera- 

Pressure 

Tempera- 

in tt)s. 

ture. 

in  tlis. 

ture. 

in  lbs. 

ture. 

in  fbs. 

ture. 

60 

295° 

69 

305° 

78 

314° 

95 

328° 

61 

296° 

70 

306° 

79 

314° 

100 

332° 

62 

298° 

71 

307° 

80 

315° 

105 

3.?5° 

63 

299" 

72 

308° 

81 

316° 

no 

339° 

54 

300° 

73 

309° 

82 

317° 

i'5 

342° 

65 

301° 

74 

310° 

83 

318° 

120 

345° 

66 

302° 

75 

3U° 

.   84 

3I90 

125 

349° 

67 

303° 

76 

312° 

85 

320° 

130 

352° 

68 

304° 

77 

313° 

90 

324° 

"  It  will  readily  be  seen  by  the  above  that  a  pressure  of  sixty 
pounds  requires  a  temperature  of  295°  by  Fahrenheit's  scale  to 
produce  it,  and  eighty-five  pounds  320°,  at  which  latter  pressure 
I  vulcanize,  running  one  hour,  and  with  the  most  satisfactory 
results. 

"  The  manner  of  putting  up  and  using  the  gauge  is  very  sim- 
ple. All  that  is  required  is  to  secure  it,  by  screws  passing 
through  the  flange  on  the  back,  in  some  conspicuous  and  con- 
venient place,  attach  a  pipe  and  carry  it  down  ten  or  twelve 
inches,  give  it  a  bend  or  curve  upward  about  half  its  length,  or 


556 


MECHANICAL    DENTISTRY. 


five  or  six  inches,  thence  at  right  angles  or  otherwise,  and  in 
any  convenient  length  not  less  than  three  feet,  to  the  vulcanizer. 

"The  annexed  cut  (Fig.  542)  is  from  a  photograph  of  a  Whit- 
ney vulcanizer  with  the  gauge  attached,  but  is  by  no  means  the 
only  arrangement  which  can  be  made,  as,  in  some  cases,  con- 
venience may  require  more  pipe  or  a  different  distribution. 

"  A,  table  or  work-bench  ;  B,  vulcanizer  ;  C,  side  outlet  pend- 
ant cock  screwed  on  in  place  of  the  thermometer  scale  ;  D, 
coupling-joint ;  E,  angle  in  the  pipe ;  F,  iron  pipe,  three- 
sixteenths  inside;  G,  U-shaped  curve,  five  or  six  inches  in 
depth ;  H,  cock  to  the  gauge  ;  I,  gauge. 

"  The  fitting,  putting  up,  and  arranging  the  entire  apparatus 

Fig.  542. 


can  be  done  in  an  hour's  time  by  any  gas-fitter,  or  to  those  re- 
siding away  from  cities  or  towns  where  such  mechanics  are 
employed,  can  be  furnished  to  order  by  them,  or  by  parties  fur- 
nishing the  gauge. 

"  All  the  joints,  from  the  vulcanizer  to  the  gauge,  except  the 
coupling,  should  be  '  leaded  '  with  very  thick  lead  paint,  and 
screwed  together  steam-tight. 

"  In  using  the  apparatus,  the  cocks,  C  and  H,  must  be  turned 
straight  with  the  pipe,  for  if  shut  off  at  either  point,  the  gauge 
cannot  be  acted  upon  by  the  steam.  I  generally  heat  the  water 
in  the  vulcanizer  nearly  or  quite  to  the  boiling  point,  and  let  off 


RUBBER    OR    VULCANITE    BASE.  557 

the  heated  air  by  turning,  or  allowing  to  remain  open,  the  cock, 
C,  then  connect  at  the  coupling,  D,  turning  the  nut  tight  with  a 
wrench. 

"  So  soon  as  steam  begins  to  form,  it  is  condensed  by  con- 
tact with  the  cold  part  of  the  pipe,  and  falls  into  and  fills  the 
curve  or  coil  with  water,  which  is  then  forced  into  the  gauge 
with  a  power  indicated  by  the  pointer  on  the  dial.  The  pipe 
should  descend  a  trifle  from  the  angle,  E,  to  the  commencement 
of  the  curve,  to  facilitate  the  passage  of  the  condensed  steam  to 
that  point. 

"Although  vulcanizing  one  hour  at  eighty-five  pounds  affords 
results  satisfactory  to  me,  others  may  prefer  a  different  time  with 
more  or  less  heat. 

"The  table  will  be  found  a  guide  in  such  cases. 

"  When  the  time  is  up,  discontinue  the  fire,  and  shut  off  the 
steam  by  turning  the  cock,  C.  Turn  the  cock,  H,  in  the  same 
manner,  to  prevent  a  too  sudden  reverse  movement  of  the 
machinery  of  the  gauge,  the  pressure  on  which  should  be  grad- 
ually relieved  at  any  convenient  time. 

"  Now  disconnect  by  unscrewing  the  coupling  and  dispose  ot 
the  steam  in  the  vulcanizer  by  blowing  off,  or  any  other  means 
preferred.  Further  remarks  would  seem  unnecessary  to  a  full 
understanding  of  the  subject.  Having  used  the  gauge  almost 
every  day  for  about  six  months,  I  am  fully  satisfied  that  it  is  a 
decided  improvement  in  vulcanizing,  and  no  reasonable  sum 
would  induce  me  to  substitute  the  thermometer." 

Another  appliance,  Avhich,  in  important  respects,  is  an  im- 
provement on  the  steam-gauge  last  considered,  is  illustrated  and 
referred  to  on  page  535. 

This  device  was  invented  by  Dr.  J.  B.  Coolidge,  of  Boston, 
about  the  year  1871.  A  number  of  them  were  made  and  sold 
at  that  time,  and  are  to-day  in  good  condition.  It  is  operated 
by  the  pressure  of  steam  upon  a  thin  metal  disk,  which,  yielding 
to  the  pressure,  closes  a  valve  which  controls  the  flow  of  gas  to 
the  burner  under  the  vulcanizer.  Extensive  experiments  have 
been  made  to  procure  a  metal  for  the  disk  which  would  not  lose 
its  elasticity  by  use,  nor  give  way  from  the  effects  of  corrosion, 
and  the  present  improved  regulator  is  offered  to  the  dental  pro- 


558  MECHANICAL    DENTISTRY. 

fession  with  the  assurance  that  it  will  be  found  to  be  accurate, 
serviceable,  and  durable. 

The  time  regulator  is  of  new  design.  In  this,  as  in  the  gas 
regulator,  the  use  of  rubber  in  any  form,  excepting  as  connect- 
ing tubing,  has  been  entirely  discarded,  as  experience  has 
proved  that  substance  to  be  very  prone  to  deterioration  from  a 
variety  of  causes.  It  has  a  metallic  valve,  which  is  gas-tight, 
whether  it  be  open  or  closed,  and  the  operating  screw  being 
protected  from  the  action  of  the  gas,  the  valve  will  be  found  to 
operate  with  ease  and  certainty.  The  timing  device  is  operated 
by  the  minute  arbor  of  the  clock,  instead  of  the  hour  arbor,  as 
is  usually  the  case;  it  is  capable  of  very  delicate  adjustment  as 
to  time,  its  variation  being  limited  by  seconds  instead  of  minutes. 

The  gas  regulator  is  a  better  means  of  maintaining  a  regular 
heat  than  a  thermometer,  for  the  reason  that  as  it  acts  by  the 
steam  pressure  its  movement  is  positive,  and  it  can  be  depended 
upon  to  act  at  the  desired  point  after  it  is  once  properly  set.  Be- 
fore the  thermometer  can  act,  it  has  to  receive  a  certain  amount 
of  heat,  and  the  rapidity  with  which  this  will  be  received 
depends  upon  the  conductivity  of  the  parts  between  the  flame 
and  the  thermometer.  There  are  several  conditions  which  will 
operate  to  vary  and  retard  the  action  of  the  thermometer. 

The  following  experiment  will  illustrate  the  comparative 
operation  of  the  two  devices  :  "  Let  the  vulcanizer  be  closed 
with,  say,  two  inches  of  water  in  it,  and  heat  applied.  The 
regulator  will  turn  down  the  gas,  when  the  thermometer 
registers  somewhere  in  the  neighborhood  of  300°.  If  the  screw 
cap  of  the  safety  disk  is  now  loosened,  and  steam  allowed  to 
escape  for  one  minute,  and  the  screw  cap  then  tightened,  the 
thermometer  will  in  a  few  minutes  be  found  to  register  320°. 

"The  reason  of  this  is  that  as  air  conducts  heat  very  imper- 
fectly, its  mixture  with  the  steam  interferes  with  its  conductivity 
and  with  the  indication  of  the  temperature  by  the  thermometer; 
but  after  the  air  has  been  allowed  to  escape,  there  is  an  atmos- 
phere of  steam  above  the  water  in  the  vulcanizer,  which  must 
be  of  the  pressure  due  to  its  temperature  throughout  its  whole 
extent." 

Removing  the  Flask  after  Vulcanizing. — When    the    pro- 


RUBBER    OR    VULCANITE    BASE.  559 

cess  of  vulcanizing  has  been  conducted  a  sufficient  length  of 
time,  the  flame  is  turned  off  and  the  steam  discharged  through 
the  safety-valve,  if  the  vuicanizer  is  provided  with  one ;  or  the  lower 
half  of  the  boiler  may  be  placed  in  cold  water  until  the  contents 
are  cooled  down  to  about  200°.  When  time  will  permit,  how- 
ever, it  is  better  to  let  the  vuicanizer  cool  gradually.  The  top 
is  then  taken  off  and  the  flasks  removed.  The  latter  should 
always  be  allowed  to  cool  gradually,  as  the  immersion  of  the 
flask,  while  hot,  in  cold  water  will  endanger  the  porcelain  teeth 
by  a  too  sudden  change  of  temperature.  Neither  should  the 
flask  be  opened  while  hot,  for  the  plate,  being  pliable  when 
heated,  would  be  liable  to  suffer  some  change  of  form  in  forcing 
the  sections  of  the  flask  apart,  or  in  removing  the  piece  after 
separation  of  the  flask.  When  the  plate  is  removed  from  the 
flask,  detach  carefully  all  adhering  plaster  with  a  pointed  knife, 
and  cleanse  well  by  washing  with  a  stiff  brush. 

The  Finishing  Process. — The  rougher  and  more  redundant 
portions  of  the  rubber  are  first  removed  with  coarse  files  or 
rasps,  following  with  those  of  a  finer  cut  (Fig.  543)  or  lathe 
burs  (Fig.  545),  until  all  parts  of  the  piece  accessible  to  such 
instruments  are  rediiced  to  nearly  the  thickness  required.  The 
excess  of  material  on  the  lingual  side  of  the  plate  and  other 
points  not  admitting  of  the  use  of  the  file  is  removed  with 
scrapers  of  various  forms,  some  of  which  are  shown  in  Fig.  544. 
After  nearly  the  desired  thickness  is  thus  obtained,  and  the 
surface  rendered  somewhat  smooth  and  uniform,  a  still  further 
reduction  is  obtained  with  the  use  of  sand-paper,  using  first  the 
coarser  and  finishing  with  the  finer  numbers.  The  final  polish 
is  then  given  to  the  surface,  first  with  the  use  of  finely  pulver- 
ized pumice-stone,  and  afterward  with  either  prepared  chalk  or 
whiting.  The  best  method  of  applying  the  pumice  is  with  flat, 
circular  pieces  of  cork  of  various  sizes,  which  may  be  readily 
formed  by  attaching  them  to  the  lathe  and  reducing  them  to  the 
proper  size  and  shape  with  a  file  while  revolving.  The  chalk 
or  whiting  may  be  applied  upon  a  cotton  or  ordinary  brush 
wheel.  In  the  use  of  the  polishing  materials,  the  latter  should 
be  kept  constantly  and  freely  saturated  with  cold  water  through- 
out the  operation. 


56o 


MECHANICAL    DENTISTRY. 


Fig.  543. 


Fig.  544. 


RUBBER  OR  VULCANITE  BASE.  56 1 

Partial  Dentures  Constructed  in  a  Base  of  Rubber. — The 
foregoing  description  of  the  method  of  forming  entire  dentures 
in  a  base  of  rubber,  together  with  a  knowledge  of  the  manner 
of  constructing  parts  of  sets  of  teeth  mounted  on  metallic 
plates,  will  render  any  extended  description  of  the  former 
process,  as  it  relates  to  partial  pieces,  unnecessary.  A  base- 
plate of  the  required  thickness  and  dimensions  is  accurately 
adapted  to  a  model  of  the  parts,  the  narrower  portions  passing 
into  the  spaces  between  the  teeth  being  stiffened  by  doubling 
the  plate  at  these  points  with  an  additional  strip  of  the  material 
used.  The  central  portion  of  the  plate  may  also  be  temporarily 
supported,  and  its  form  preserved,  by  filling  in  the  concavity 
with  a  layer  of  stiffened  wax.  A  rim  of  wax  is  then  attached 
in  the  usual  manner  to  those  portions  of  the  plate  occupying 
the  vacuities  on  the  ridge,  when  the  plate  is  placed  in  the  mouth 
and  an  impression  of  the  points  of  the  opposing  teeth  secured  ; 
it  is  then  removed,  reapplied  to  the  model,  and  the  heel  of  the 
latter  extended  posteriorly  to  form  an  articulating  surface  for  the 
remaining  portion  of  the  antagonizing  model — the  latter  being 
formed  in  the  ordinary  way.  The  teeth  are  then  fitted  to  the 
vacuities  in  precisely  the  same  manner  as  when  metallic  plates" 
are  used,  and  the  wax  trimmed  to  the  required  fullness.  The 
plate,  with  the  teeth  attached,  is  then  placed  in  the  mouth  and 
any  necessary  corrections  made  in  the  arrangement  of  the  teeth  ; 
after  which  it  is  remoV^ed  and  readjusted. 

In  constructing  partial  sets  of  vulcanite,  it  is  of  the  first  im- 
portance, when  forming  the  mold,  that  the  relation  of  the  porce- 
lain teeth  to  the  model  of  the  mouth  should  be  accurately  main- 
tained, the  reasons  for  which  are  fully  set  forth  when  treating  of 
the  formation  of  the  mold  or  matrix  for  full  sets.  To  secure 
this  result  with  certainty,  the  following  method  should  be 
adopted.  Having  adjusted  the  plate  and  teeth  upon  the  model, 
with  the  wax  trimmed  and  carved  to  the  required  fullness,  place 
the  model  in  the  lower  section  of  the  flask  and  fill  in  with  plaster, 
extending  it  up  to  the  points  of  the  teeth,  binding  them  to  the 
model,  and  making  the  line  of  separation  of  the  sections  of  the 
flask  at  that  point.  The  ends  of  the  plaster  teeth  should  be  cut 
away  sufficiently  to  allow  of  a  ready  separation  of  the  sections. 
36 


562  MECHANICAL    DENTISTRY. 

Plaster  is  then  poured  in  for  the  upper  section  of  the  mold,  and, 
when  hard,  the  flask  is  parted  and  the  wax  removed  from  the 
model  and  teeth,  the  latter  being  retained  in  the  lower  instead  of 
the  upper  section  as  in  fall  cases. 

Metallic  Clasps  Attached  to  Rubber  Plates.— Although 
atmospheric  pressure  or  adhesion  should  be  made  available  in 
all  practicable  cases  as  a  means  of  retaining  parts  of  sets  of  teeth 
in  the  mouth,  yet  cases  occasionally  present  themselves  necessi- 
tating the  employment  of  clasps.  These  may  be  of  rubber,  but 
those  formed  of  gold,  or  gold  alloyed  with  platinum,  are  more 
reliable  and  better  adapted  to  those  cases  where  the  spaces  be- 
tween the  teeth  are  contracted.  The  following  description  of 
the  method  of  constructing  them  is  given  by  Prof  Wildman  : — 

"  First  bend  the  clasp  to  fit  the  tooth  accurately  ;  then  make 
the  attachment  by  which  it  is  to  be  held  to  the  rubber  (this  may 


be  done  by  soldering  a  thin  plate  of  gold  or  platina  to  the  clasp 
in  such  a  position  that  it  will  be  inclosed'  in  the  rubber) ;  then 
perforate  the  plate  with  numerous  small  holes,  which  should  be 
countersunk  on  both  sides  (Fig.  546).  This  plate  entering  the 
base,  the  rubber  filling  the  holes  forms  pins  which  rivet  the  clasp 
securely  to  the  rubber  plate. 

"  Or  the  attachment  may  be  made  in  this  manner :  On  the 
parts  of  the  clasp  that  can  be  covered  with  rubber  drill  one,  two, 
or  three  holes,  as  the  space  may  admit;  insert  gold  or  platina 
wire,  solder  with  gold  solder,  then  cut  off  at  proper  length,  and 
head  them  (Fig.  547);  these  act  in  retaining  the  clasp  in  the 
same  manner  as  the  double-headed  pins  in  securing  the  tooth  to 
the  base,  and  offer  the  advantage  over  the  perforated  plate  of 
being  more  easily  manipulated  and  less  liable  to  become  dis- 
placed in  packing  the  mold.     The  clasp  is  to  be  attached  to  the 


RUBBER  OR  VULCANITE  BASE.  563 

model  plate,  and  will  remain  secured  in  the  mold  when  it  is 
opened." 

A  metallic  clasp  may  also  be  very  securely  attached  to  the 
rubber  by  drilling  a  number  of  holes  in  that  part  of  the  clasp 
which  lies  in  contact  with  the  rubber,  and  countersinking  them 
well  on  the  inside  of  the  clasp. 

Substitution  of  Plate  for  Rubber  Teeth. — An  ordinary 
plate  tooth,  such  as  is  commonly  used  in  connection  with  a 
metallic  plate-base,  can  be  readily  rendered  suitable  for  a  rubber 
base.  This  is  done  by  soldering  a  narrow  strip  of  gold  plate  to 
the  ends  of  the  platinum  pins,  forming  a  loop  or  staple  (Fig. 
548),  and  which,  embedded  in  the  rubber,  renders  the  attachment 
very  secure.  A  narrow  arm  of  rubber  extending  to  a  single 
tooth  may  be  materially  strengthened  by  permitting  the  gold 
strip,  perforated  with  holes  or  roughened  on  its  edges,  to  pass 
some  distance  into  the  rubber,  as  seen  in  Fig.  549. 

Fig.  548.  Fig.  549. 


Instead  of  forming  a  loop  or  staple  as  mentioned,  it  will  be 
preferable  in  many  cases  to  solder  to  the  tooth  a  somewhat 
wider  strip  than  that  represented,  in  the  same  manner  as  ordinarily 
practised  in  backing  for  gold  work,  the  strip  being  strengthened 
by  flowing  solder  at  the  angle  of  divergence  from  the  heel  of  the 
tooth,  and  extending  ihence  into  the  body  of  the  rubber,  per- 
forated or  roughened  on  the  edges  as  before  recommended. 
The  rubber  in  this  case  may  be  cut  away,  when  finishing,  to  the 
angle,  leaving  nothing  but  the  strip  of  gold  and  sub-lining  of 
rubber  at  the  base  of  the  tooth.  This  method  may  be  resorted 
to  with  signal  advantage  in  those  cases  where,  on  closure  of  the 
jaws,  the  points  of  the  opposing  teeth  encroach  unduly  upon 
the  space  to  be  filled,  extending  nearly  to  the  gum,  requiring 
the  tooth  of  replacement  to  be  as  thinly  formed  throughout  its 
length  as  possible. 

Repairing. — If   a  tooth   or  block   has   been   broken,   or   any 


564  MECHANICAL    DENTISTRY. 

change  is  to  be  made  in  the  position  of  either,  the  teeth  or  frag- 
ments thereof  are  removed,  and  an  irregularly  shaped  groove  or 
dove-tail  formed  in  the  base  occupying  the  space  to  be  supplied  ; 
into  this  space  the  tooth  or  teeth  are  properly  arranged  and  sup- 
ported with  wax  ;  the  dove-tail  is  then  filled  in  with  wax,  giving 
some  additional  fullness  to  compensate  for  waste  in  finishing. 
All  portions  of  the  piece  except  the  lingual  face  of  the  plate  and 
teeth  are  then  embedded  in  plaster  in  the  lower  section  of  the 
flask.  The  upper  section  of  the  mold  is  obtained  in  the  usual 
way.  When  separated  and  all  traces  of  wax  removed,  the  gum 
is  packed  into  the  cavity  around  the  tooth  or  teeth.  Grooves 
are  then  cut  extending  out  from  the  mold,  the  two  sections 
heated  and  forced  together,  and  the  process  of  vulcanizing  con- 
ducted in  the  usual  manner,  the  same  time  and  degrees  of  heat 
being  required  as  in  the  first  instance.  The  renewed  heat  em- 
ployed renders  the  surface  of  the  material  previously  vulcanized 
somewhat  darker,  to  remove  which  it  is  recommended  to  moisten 
the  surface  with  dilute  nitric  acid  for  a  short  time,  after  which 
the  piece  is  thoroughly  washed,  and  then  placed  for  a  few  min- 
utes in  an  alkaline  solution  to  remove  any  remaining  traces  of 
acid.  It  is  also  recommended  to  immerse  the  case  in  alcohol  for 
five  or  six  hours,  and  then  expose  it  to  the  rays  of  the  sun  for  a 
like  period  of  time. 

Dr.  A.  A.  Blount,  of  Geneva,  Switzerland,  in  the  Oliio  State 
Journal,  suggests  the  following  method  of  replacing  a  broken 
crown  without  removing  the  entire  section.  "  Finding  it  im- 
possible to  match  the  injured  block,"  he  says:  "  I  ground  the 
broken  tooth  down  to  the  gum,  as  one  would  for  a  pivot  tooth, 
and,  as  I  had  often  done  before  in  mending  a  continuous-gum 
piece,  selecting  a  plain  rubber  tooth  the  exact  size  and  shape, 
ground  it  carefully  and  accurately  to  fit,  cementing  it  in  place 
with  a  plastic  cement,  which  served  to  hold  it  firm  and  prevent 
the  rubber  from  coming  through  to  the  front.  The  plate  being 
prepared  as  usual  for  mending,  the  piece  was  vulcanized.  After 
being  finished,  no  one  coulS  tell  that  the  block  had  ever  been 
mended.  This  method  of  repairing  broken  blocks,  mounted 
upon  Watt's  metal,  will  be  found  very  practical,  as  it  is  some- 
what difficult  to  replace  a  broken  block  upon  that  base." 


RUBBER    OR    VULCANITE    BASE.  565 

Tlie  whole  subject  of  repairing  rubber  plates  is  so  fully  and 
clearly  described  by  Dr.  George  R.  Snow,  in  an  article  entitled, 
"  Repairing  Vulcanite  Plates,"  that  his  processes  are  here  given 
in  detail.  The  writer  would  premise  that  he  has  long  since 
abandoned  the  older  methods  of  "  dove-tailing  "  or  "  under- 
cutting" in  repairing  rubber  plates,  and  would  emphasize  what  is 
stated  by  Dr.  Snow,  "  that  perfect  union  can  be  obtained  in  such 
cases  if  the  surfaces  of  contact  are  freshly  cut,  absolutely  clean, 
and  properly  roughened." 

"  It  is  not  unusual  to  see  vulcanite  plates  which  have  been 
cracked  or  broken,  and  repaired  by  what  may  be  termed  the 
'  hole  and  plaster'  system.  Holes  are  drilled  through  the  plate 
along  the  edges  of  the  crack,  and  a  new  thickness  of  rubber  su- 
perimposed upon  a  mass  which,  possibly,  is  already  too  thick  for 
comfort  or  convenience,  the  old  crack  still  remaining  as  a  weak 
point  to  occasion  further  breakage.  No  advantage  was  taken  of 
any  possibility  of  union  between  the  old  and  new  material,  the 
dentist  having  been  obviously  ignorant  of  the  fact  that  perfect 
union  can  be  obtained  in  such  cases  if  the  surfaces  of  contact 
are  freshly  cut,  absolutely  clean,  and  properly  roughened. 

"  The  great  point  to  be  remembered  in  repairing  or  making 
any  addition  to  a  vulcanite  plate  is,  that  the  new  and  old  material 
will  unite  perfectly,  and  with  such  firm  adhesion  that  the  plate 
will  be  practically  as  good  as  new,  if  the  surfaces  of  the  old 
l)late  where  union  with  the  new  material  is  desired  are  freshly 
filed,  absolutely  clean,  properly  roughened,  and  of  sufficient  area. 
To  ensure  these  results,  wax  should  not  be  melted  upon  the  sur- 
faces of  union  in  waxing  up,  and  removal  of  the  wax  from  the 
mold  should  be  accomplished  by  means  of  instruments,  and  not 
by  hot  water,  unless,  possibly,  for  the  removal  of  very  small 
particles  which  cannot  otherwise  be  gotten  rid  of.  Any  amount 
of  the  old  material  desired  may  be  cut  away,  and  its  place  sup- 
plied by  new ;  and  thus  any  change  wished  may  be  effected. 
In  case  of  breakage  or  cracking,  the  plate  should  be  cut  away 
so  that  the  old  defects  will  be  wholly  obliterated  and  new 
material  supplied. 

"  As  a  first  instance,  suppose  a  partial  lower  plate,  supplying 
the  loss  of  the  bicuspids  and  molars  on  both  sides  of  the  mouth. 


566  MECHANICAL    DENTISTRY. 

to  be  broken  through  the  bar  which  extends  from  one  side  of 
the  mouth  to  the  other  behind  the  incisors.  The  fracture  is  gen- 
erally a  clean  one,  resembling  that  of  glass  or  porcelain,  and  the 
two  pieces  may  be  brought  into  apposition  with  certainty.  The 
dentist  holding  the  parts  together  in  exactly  the  right  position, 
the  assistant  covers  the  lingual  side  of  the  plate  at  the  point  of 
fracture  with  a  few  drops  of  hot  shellac  from  a  shellac  stick.  A 
little  cold  water  follows,  and  the  two  parts  of  the  plate  are  firmly 
cemented  together.  A  brace  is  now  extended  across  from  the 
molars  on  one  side  to  those  on  the  other,  by  laying  a  burnt 
match  on  the  grinding  surfaces  of  the  respective  teeth,  and  fast- 
ening both  ends  with  a  few  drops  of  hot  wax.  By  this  means 
sufficient  strength  is  obtained  to  allow  of  the  plate  being  safely 
handled.  A  piece  of  paper  or  sheet  wax  is  cut  to  fit  and  reach 
across  the  lingual  space  at  the  lower  edge  of  the  plate,  and  fas- 
tened therein  with  wax,  a  coat  of  shellac  varnish  is  applied  to 
the  paper,  the  surface  lathered  with  soap-suds,  and  rinsed,  and  a 
model  run  in  the  same  manner  as  in  filling  an  impression. 

"  After  this  has  hardened,  the  plate  is  removed  from  the  model, 
which  is  then  given  a  coating  of  liquid  silex.  This  is  always 
preferably  done  in  repairing  plates,  at  the  time  when  the  plate  is 
first  removed  from  the  model.  The  rubber  bar  may  now  be  cut 
away,  on  either  side  of  the  fracture,  by  a  jeweler's  saw,  the  cut 
being  made  diagonally,  so  as  to  make  what  is  termed  a  'scarf 
joint.  The  surfaces  should  be  further  roughened  by  making  a 
series  of  shallow  parallel  cuts  across  them  with  the  saw,  a 
thick  separating  file,  or  a  thin  wheel-bur.  The  parts  of  the 
plate  are  then  placed  upon  the  model,  waxed  up,  and  flasked, 
the  model  and  buccal  surfaces  of  the  teeth  being  covered  with 
plaster,  and  the  parting  made  so  that  the  plate  will  be  retained 
upon  the  model,  while  the  pieces  of  the  bar  can  be  readily 
removed.  After  the  flask  is  opened,  the  pieces  are  removed,  the 
usual  gateways  cut,  and  the  packing,  vulcanizing,  and  finishing 
done  as  usual. 

"  In  the  case  of  an  entire  lower  set  broken  through  the  center, 
it  will  be  seen  that  the  same  directions  will  apply,  excepting  as 
to  the  amount  of  rubber  to  be  cut  away.  A  free  cut  should  be 
made  on  the  lingual  side,  extending  through  under  the  teeth,  to 


RUBBER    OR    VULCANITE    BASE.  567 

and  including  the  labial  band  ;  so  that  the  broken  surfaces  will 
be  entirely  obliterated,  and  at  least  one-eighth  inch  in  width  of 
new  rubber  supplied  between  the  cut  surfaces.  An  engine-bur 
will  do  much  of  this  work  nicely,  and  a  wheel-bur  is  very  con- 
venient for  the  purpose  of  scoring  the  surface.  Making  the 
model,  flasking,  and  packing  will  be  done  as  before. 

"  If  one  of  the  incisor  blocks  be  broken,  and  needs  replace- 
ment, a  new  one  can  be  fitted  after  the  model  is  obtained,  and  the 
remaining  steps  of  the  process  followed  as  has  been  described. 

"  Upper  plates  are  sometimes  cracked  in  the  center,  the  crack 
extending  from  under  and  between  the  incisor  teeth  backward 
over  the  palate.  This  often  happens  from  the  amount  of  rubber 
just  behind  the  incisors  being  insufficient.  It  is  not  unusual  to 
see  it  cut  away  at  this  point,  so  that  the  pins  are  almost  or  quite 
exposed,  the  plate  having  its  usual  thickness  at  a  very  short  dis- 
tance behind  the  teeth.  A  much  larger  amount  of  material  will 
be  tolerated  here  than  is  usually  employed,  and  often  with  ben- 
efit, not  only  to  the  strength  of  the  plate  but  to  the  articulation 
of  the  wearer.  The  curve  of  the  surface  of  the  plate  should  be 
made  to  resemble  that  of  the  palate  before  the  removal  of  the 
teeth,  and  it  will  be,  found  that  the  extra  thickness  may  extend 
for  half  an  inch  behind  the  teeth  without  aimoyance  to  the 
patient. 

"  A  proper  curvature  to  the  surface  of  the  plate,  just  behind 
the  incisors,  will  do  much  to  prevent  the  disagreeable  whistling 
in  making  the  s  sound,  and  will  assist  in  giving  the  correct  enun- 
ciation to  s/i,  zJi,  and  other  Unguals. 

"  If  the  cracked  plate  fits  a  flat  mouth,  a  model  can  often  be 
drawn  from  it  as  it  is;  but  if  the  arch  is  high,  and  the  gums  pro- 
jecting, it  is  better,  after  thoroughly  cleansing  and  drying  the 
plate,  to  finish  the  cracking  by  breaking  the  plate  entirely  in 
two.  The  two  halves  may  now  be  fastened  together  by  drop- 
ping shellac  upon  the  lingual  side,  and  a  model  secured,  from 
which  either  half  of  the  plate  can  be  easily  removed.  The  whole 
palatal  portion  of  the  plate  can  then  be  removed  by  a  saw  cut. 
leaving  only  a  narrow  margin  on  the  lingual  surface  inside  the 
teeth.  The  remainder  of  the  surfaces  of  fracture  are  cut  away 
as  directed  in  case  of  the  lower  plate,  the  new  surfaces  rough- 


568  MECHANICAL    DENTISTRY. 

ened,  the  pieces  of  the  old  plate  replaced  upon  the  model  (which 
has  received  its  coating  of  liquid  silex),  waxed  up,  flasked, 
packed,  and  vulcanized,  the  teeth  being  retained  upon  the  model 
as  before  described.  The  plate,  when  finished,  will  show  the  old 
rim  and  a  margin  of  the  old  rubber  inside  the  teeth. 

"  It  is  sometimes  desirable  to  change  the  substance  of  the  plate 
entirely,  as  in  case  of  supposed  mercurial  poisoning  by  red 
rubber ;  or  at  least  to  put  what  red  rubber  there  may  be  about 
the  plate  entirely  out  of  sight,  and  to  reduce  its  quantity  to  a 
minimum.  If  this  is  to  be  done  to  the  plate  last  under  consid- 
eration, it  should  be  prepared  for  flasking  as  described,  excepting 
that  the  labial  band  should  be  cut  away,  and  everything  arranged 
so  that  the  plate  can  be  separated  from  the  model  when  flasked. 
The  parts  cutaway  should,  of  course,  be  replaced  by  wax.  The 
case  is  now  set  in  the  flask  so  as  to  leave  the  parting  at  the 
upper  edges  of  the  gums.  The  plaster  is  varnished  and  oiled, 
and  more  plaster  built  on  against  the  labial  sides  of  the  teeth, 
extending  from  their  cutting  edges  to  the  edge  of  the  flask,  and 
again  varnished  and  oiled,  so  that  the  appearance  will  now  be 
precisely  similar  to  a  plate  flasked  so  as  to  be  retained  upon  the 
model.  The  ring  of  the  flask  is  now  put  in  place  and  filled,  and 
the  plaster  allowed  to  harden. 

"  When  the  flask  is  separated,  the  teeth  will  be  found  in  its 
ring  section.  A  few  blows  of  the  hammer  will  dislodge  them, 
with  the  piece  of  plaster  built  against  their  labial  surfaces.  This 
is  carefully  broken  away,  in  two  pieces,  if  possible,  which  are 
preserved,  and  the  teeth  and  rubber  encasing  them  are  left.  The 
rubber  is  now  filed  away  as  much  as  is  practicable,  leaving  none 
of  the  old  rubber  in  sight,  and  removing  enough  from  the  palatal 
surface  to  make  a  new  fit  to  the  model.  The  teeth  and  plaster 
are  replaced  in  the  flask,  and  the  case  is  ready  for  packing  and 
vulcanizing ;  when  finished,  none  of  the  old  rubber  will  be 
seen,  and  the  plate  will  be  practically  as  good  as  though  the 
teeth  had  been  removed  from  the  old  plate  and  reset. 

"  It  is  evident  that  the  change  from  red  to  black  rubber  just 
described  can  be  made  with  a  whole  plate  or  a  broken  one  indif- 
ferently. If  a  change  of  articulation  and  a  new  fit  to  the  mouth 
is  also  desired,  on   account  of  shrinkage  of  the  gums,  the  plate 


RUBBER    OR    VULCANITE    BASE.  569 

should  be  prepared  so  as  to  draw  from  the  model,  and  a  few 
small  pieces  of  wax  put  in  the  palatal  side  to  bear  upon  the 
alveolar  ridge,  and  give  the  right  articulation  by  trial  in  the 
mouth,  the  center  of  the  plate  being  cut  away  to  facilitate  the 
fitting  of  the  plate  to  the  model.  A  fresh  model  of  the  mouth 
being  secured  from  an  impression,  the  plate  is  waxed  on  to  it, 
the  case  is  flasked  with  a  false  piece  of  plaster  built  against  the 
labial  sides  of  the  teeth,  as  has  been  described,  and  the  plate 
removed  and  cut  away  as  much  as  desired,  a  considerable 
amount  being  always  taken  from  its  palatal  surface. 

"  This  process  does  all  and  more  than  is  specified  in  the  Hyatt 
patent,  as  it  not  only  gives  a  new  fit,  but  allows  the  material  of 
the  plate  to  be  substantially  changed.  Holes  and  dove-tails,  it 
will  be  seen,  are  wholly  unnecessary,  and  the  fine  serrated  edge 
left  by  cross-cutting  the  surfaces  of  union  will  be  found  an  ex- 
cellent guide  in  scraping  the  plate  to  avoid  overlaps.  The  use 
of  shellac  as  a  cement  is  strongly  advised  in  repairing,  as  it  is 
rigid  and  brittle  when  cold,  and  the  broken  parts,  if  once  prop- 
erly brought  together,  cannot  get  out  of  adjustment  without  at 
once  attracting  attention  by  the  breakage  of  the  cement.  Wax 
does  not  answer  the  purpose  nearly  so  well. 

"  The  amount  of  shrinkage  in  rubber,  from  cooling  after  vul- 
canization, is  not  so  generally  noticed  and  provided  for  as  it 
should  be.  Plates  composed  of  single  teeth  do  not  give  trouble 
from  this  cause,  but  full  plates,  on  which  sections  are  mounted, 
are  often  very  vexatious  to  the  dentist,  from  the  changes  of 
shape  they  undergo  from  shrinkage. 

"  The  reason  of  this  is,  that  the  ends  of  the  sections  abutting 
form  an  arch  of  porcelain,  which  expands  or  contracts  but  slightly 
from  changes  of  temperature.  The  rib  of  vulcanite  immediately 
inside  this  arch,  and  in  which  the  pins  are  embedded,  forms  a 
second  arch,  closely  attached  by  the  pins  to  the  first  one.  The 
plate  is  molded  to  the  model,  and  hardened  at  a  temperature  of 
about  320°,  and  is  afterward  placed  in  the  mouth,  where  the 
temperature  is  in  the  neighborhood  of  90°.  Under  these  circum- 
stances the  contraction  of  the  rubber  which  ensues  has  the  effect 
of  lessening  the  radius  of  the  arch,  drawing  the  heels  of  the 
plate  together,  thus   rendering  it  a  little   too   narrow  to  fit  the 


570  MECHANICAL    DENTISTRY. 

mouth  accurately.  This  has  the  further  effect  of  elevating  the 
palatal  portion  of  the  plate,  which,  when  tried  in  the  mouth,  will 
usually  be  found  to  rock  slightly, — often  so  much  so  as  to  inter- 
fere with  its  fitting. 

"  If  the  plate  has  been  made  upon  a  model  taken  from  the 
mouth,  the  difficulty  is  overcome  by  warming  the  back  part  of 
its  palatal  portion,  pressing  it  down  slightly,  and  cooling  it  while 
the  pressure  is  continued,  the  narrowing  of  the  plate  being  too 
small  in  amount  to  be  of  itself  objectionable. 

"  This  change  can  be  accomplished  with  more  certainty  by 
making  a  small  plaster  cast  of  the  palatal  portion  of  the  plate, 
placing  upon  the  part  where  the  change  is  desired  a  small  piece 
of  folded  paper,  folded  so  as  to  present  a  thick  center,  and  forc- 
ing the  plate  down  upon  it  after  its  palatal  portion  has  been 
heated. 

"The  shrinkage  here  alluded  to  becomes  a  more  serious 
matter  when  the  plate  is  re-vulcanized,  in  the  course  of  repairing 
it.  It  is  flasked  when  the  change  in  form  by  its  shrinkage  has 
already  once  manifested  itself,  and  again  heated  to  320°;  and  in 
cooling  a  second  shrinkage  takes  place,  it  becomes  still  narrower, 
and  its  fit,  already  defective,  is  made  perceptibly  worse.  It  now 
often  becomes  a  matter  of  necessity  to  bring  it  back  to  its  proper 
shape  before  it  can  be  worn  with  comfort.  To  provide  for  this, 
a  small  dot  should  be  made  with  a  pointed  instrument  on  each 
side  of  the  plate,  immediately  behind  the  molars,  and  a  pair  of 
dividers  set  to  the  distance  between  these  points.  After  vulcan- 
ization, the  dividers  can  be  applied  to  the  marks,  and  they  will 
indicate  the  amount  of  shrinkage  the  plate  has  experienced. 
Let  the  plate  now  be  warmed  just  behind  the  incisors,  and  in 
the  mesial  line,  by  repeated  short  puffs  of  a  blowpipe  flame. 
This  must  be  done  carefully,  and  the  heat  not  allowed  to  extend 
over  an  area  much  exceeding  half  an  inch  in  diameter.  When 
the  rubber  is  sufficiently  softened,  the  plate  should  be  taken  by 
the  heels,  a  pull  made  upon  it  sufficiently  forcible  to  expand  the 
arch,  and  a  stream  of  cold  water  applied.  The  dividers  will  at 
once  show  if  the  change  made  is  sufficient. 

"  When  the  plate  is  now  tried  in  the  mouth,  it  maybe  that  the 
back  edge  will  not  touch  the  roof,  and  air  will  be  admitted  under 


RUBBER    OR    VULCANITE    BASE.  57 1 

the  plate  ;   in  which  case  the  back  edge  should  be  heated  and 
forced  up  to  its  proper  position. 

"  The  same  remarks  apply  to  full  lower  plates  as  well,  which 
often  are  found  to  have  lost  their  fit  in  a  measure,  after  having 
been  revulcanized.  The  process  above  detailed  will  suffice  to 
restore  them  to  their  former  fit,  and  render  them  again  comfort- 
able to  the  wearer." 


CHAPTER  XIV. 
CELLULOID    BASE. 

The  employment  of  celluloid  in  prosthetic  dentistry,  notwith- 
standing the  very  general  failure  which  attended  its  first  intro- 
duction into  practice,  came  rapidly  into  general  professional 
favor  as  a  cheap,  convenient,  and  serviceable  base  for  artificial 
dentures.  With  the  more  recent  improvements  in  the  manu- 
facture and  seasoning  of  blanks,  more  perfectly  adapted  appli- 
ances for  molding,  and  a  more  extended  acquaintance  with  the 
peculiar  and  distinctive  characteristics  of  this  material,  it  has,  in 
the  practice  of  many,  superseded,  in  a  great  measure,  other 
plastic  vegetable  substances  for  the  purpose  indicated. 

That  celluloid  possesses  many  important  qualities  which  com- 
mend its  emplo3^ment  as  a  base  in  preference  to  rubber  can 
hardly  be  questioned.  It  is  more  in  harmony  with  the  soft  tis- 
sues of  the  mouth,  more  cohesive  in  texture,  approximates  more 
nearly  the  natural  gum  color,  contains  far  less  vermilion  pigment 
in  its  composition,  and  is  less  objectionable  by  reason  of  the 
comparative  cleanliness  accompanying  its  manipulation. 

The  chief  objection  urged  against  celluloid  as  a  base  is  its  low 
power  of  transmitting  caloric,  but  it  is  believed  to  be  less  objec- 
tionable in  this  respect  than  rubber.  Both  are  poor  conductors, 
and  the  soft  tissues  of  the  mouth  in  contact  with  either  suffer,  in 
some  degree,  as  a  consequence  of  this  property. 

Celluloid,  as  at  present  produced,  and  when  properly  manipu- 
lated, does  not,  in  any  appreciable  degree,  undergo  change  of 
form  after  molding  by  warping  either  in  or  out  of  the  mouth,  as 
was  formerly  the  case,  nor  does  it  absorb  the  oral  secretions.  It 
loses  somewhat  the  freshness  and  clearness  of  its  original  pink 
color,  however,  after  having  been  in  use  for  some  time,  in  many 
cases  in  a  very  marked  degree. 

Though    not   bearing  so   perfect   a  resemblance  to  the  com- 

572 


CELLULOID    BASE.  573 

plexion  of  the  healthy  gum  tissue  as  the  porcelain  imitations, 
yet  the  near  approximation  of  celluloid  to  the  desired  color 
makes  the  use  of  single  plain  teeth  admissible  for  permanent 
dentures,  and  this  is  unquestionably  its  crowning  merit,  and 
makes  it  the  most  desirable  of  all  the  so-called  "  cheap  bases." 
The  indiscriminate  and  almost  universal  employment  of  block 
or  sectional  gum  teeth  in  connection  with  rubber  has  done 
more  to  degrade  the  prosthetic  department  of  dental  practice 
than  all  other  causes  combined.  The  optional  arrangement 
of  each  individual  tooth  to  meet  the  requirements  of  special 
cases  in  respect  to  expression,  articulation,  and  antagonism 
is  one  of  the  absolute  and  indispensable  requirements  of  a 
perfect  artificial  denture.  A  rruore  general  recognition  of  this 
important  fact  must,  sooner  or  later,  lead  to  the  entire  abandon- 
ment of  rubber  in  connection  with  "  ready-made  "  sectional  gum 
teeth.  "Taking  into  view  all  its  qualities,"  says  a  well-known 
writer,  "and  leaving  out  the  question  of  freedom  from  monopo- 
lies, the  conclusion  is  that  celluloid  has  the  potentialities  which 
should  dethrone  rubber,  and  establish  itself  as  the  best  of  the 
cheap  bases." 

Composition  and  Manufacture. — The  following  is  the  sub- 
stance of  Prof.  Charles  J.  Essig's  account  of  the  composition  and 
manufacture  of  celluloid  : — 

Celluloid  is  derived  from  cellulose,  a  woody  fiber,  constituting 
the  framework  or  foundation  of  plants. 

Linen,  cotton-wool,  hemp,  etc.,  are  examples  of  cellulose.  For 
the  manufacture  of  celluloid,  the  cellulose  is  first  converted  into 
paper;  hemp  is  the  form  of  cellulose  employed  for  this  purpose, 
because  it  has  been  found  to  make  the  strongest  paper,  and  the 
stronger  the  paper  the  better  the  celluloid. 

The  hemp  is  first  converted  into  paper  in  the  usual  way  by 
paper  machines.  By  this  process  the  form  of  the  material  un- 
dergoes a  physical  change  only,  while  chemically  it  remains  the 
same,  viz.,  nearly  pure  cellulose,  and  has  a  formula  of  CeHioO.v 
The  cellulose,  now  in  the  form  of  hemp-paper,  is  converted  into 
pyroxylin  by  a  process  technically  known  as  "  conversion," 
this  change  being  effected  by  immersing  the  hemp-paper  in  a 
strong    mixture  of  nitric  and    sulphuric    acids  for    a  sufficient 


574  MECHANICAL    DENTISTRY. 

length  of  time,  when  it  is  removed  from  the  acids  and  washed 
thoroughly. 

It  is  now  still  in  the  form  of  paper,  but  it  will  be  found  to  have 
increased  in  weight  about  seventy  per  cent.,  and  to  have  become 
highly  explosive,  taking  fire  at  about  3CXD°  F. 

Pyroxylin,  then,  is  the  chief  ingredient  in  celluloid,  and  is 
reduced  to  a  pulp  in  a  machine  similar  to  that  used  in  paper- 
making;  a  thorough  mixture  is  then  made  of — 

Pyroxylin, lOO  parts. 

Camphor,      .         40       " 

Oxid  of  zinc, 2      " 

Vermilion, • 0.6  " 

Some  alcohol  is  used  to  soften  the  camphor.  The  mass  is  now 
put  under  a  hydraulic  pressure  of  two  thousand  pounds  to  the 
square  inch.  The  cylinders  in  which  it  is  pressed  have  a  small 
orifice  in  the  side  near  the  bottom,  and  when  pressure  is  made 
the  celluloid  is  forced  out  through  this  orifice. 

The  immense  pressure  is  to  condense  or  solidify  the  celluloid, 
and  as  it  is  forced  out  it  is  cut  off  in  pieces  of  the  proper  size, 
and  molded  by  pressure  and  heat  to  the  forms  in  which  we  re- 
ceive it.  At  this  point  the  blanks  are  still  soft,  and  require  to  be 
seasoned  ;  this  requires  about  two  months,  during  which  time 
they  are  kept  in  a  room  at  a  temperature  of  160°  F. 

Processes  Preliminary  to  Molding. — While  many  of  the 
processes  entering  into  the  construction  of  artificial  dentures, 
with  celluloid  as  a  base,  are  essentially  the  same  as  those  required 
when  rubber  is  used,  yet  there  are,  in  many  important  respects, 
modifications  of  practice  made  necessary  by  the  peculiar  nature 
and  behavior  of  the  material  employed. 

When  the  distinctive  characteristics  of  celluloid  are  well  un- 
derstood, and  the  operator  is  familiar  with  the  approved  methods 
of  working  it,  no  unusual  difficulties  attend  its  successful  mani- 
pulation. To  attain  uniformity  and  satisfactory  results,  how- 
ever, it  is  absolutely  necessary  that  there  should  be  a  faithful 
compliance  with  every  manipulative  detail,  however  seemingly 
unimportant,  which  experience  in  the  use  of  this  substance  has 
demonstrated  to  be  essential. 


CELLULOID    BASE.  575 

Plaster  Model. — The  inferior  plasticity  of  celluloid,  compared 
with  vulcanizable  rubber,  when  exposed  to  the  action  of  heat, 
and  the  consequent  greater  pressure  necessary  to  mold  it  into 
any  given  form,  makes  it  necessary  to  give  to  the  plaster  model 
the  greatest  practicable  hardness  and  strength.  To  secure  these 
important  qualities  it  is  recommended  to  use  the  best  quality  of 
coarse  builder's  plaster,  which,  though  it  does  not  set  so  quickly 
as  the  finer  and  whiter  varieties,  becomes  much  harder  and 
more  resistant  to  pressure  when  thoroughly  dried.  Increased 
hardness  will  be  secured  by  adding  to  the  plaster  mixture  a  small 
quantity  of  clean  white  river  or  lake  sand  or  marble  dust. 

A, smoother  face  will  be  given  to  the  model  by  first  coating 
the  surface  of  the  impression  with  a  moderately  thin  mixture  of 
fine  plaster,  and  as  this  begins  to  set,  fill  in  with  the  coarser 
variety  for  the  body  of  the  model. 

The  plaster  for  the  model  should  be  mixed  as  thick  as  can  be 
well  poured,  taking  care,  as  it  is  slowly  introduced,  to  expel  any 
confined  air  by  tapping  or  shaking  the  impression-tray  as  the 
plaster  flows  in. 

In  cases  where  there  is  any  considerable  anterior  projection  of 
the  alveolar  ridge  in  front,  above  or  below,  the  corresponding 
portion  of  the  plaster  model  is  liable  to  be  crushed  under  the 
pressure  necessary  to  mold  celluloid.  To  prevent  such  accident, 
it  has  been  recommended,  in  addition  to  the  expedient  to  be 
mentioned  hereafter,  to  place  in  the  front  part  of  the  impression 
a  curved  piece  of  brass  plate  punched  full  of  holes,  one-half  or 
three-fourths  of  an  inch  wide,  which,  when  the  impression  is 
filled,  will  be  embedded  in  the  central  portion  of  the  plaster  ridge, 
and  extend  some  distance  into  the  body  of  the  model. 

Metal  Casts. — In  extreme  cases,  where  the  ridge  is  very  thin 
and  the  projection  spoken  of  excessive,  it  is  safer  and  better 
practice  to  substitute  metal  for  plaster  in  forming  the  model.  In 
this  case  the  latter  may  be  obtained  by  pouring  block-tin  or 
Babbitt  metal  directly  into  the  plaster  impression,  which  should 
first  be  thoroughly  dried,  and  the  cavity  for  the  air-chan  ber 
formed  before  pouring. 

A  solid  metal  cast,  however,  should  never  be  employed  when 
there  is  any  considerable   undercuitmg,  as  is   often  the  case  on 


576  MECHANICAL    DENTISTRY. 

either  side  of  the  median  line  in  front,  forming  the  canine  fossa, 
and  posteriorly  underneath  the  maxillary  tuberosities,  since,  ki 
such  cases,  it  will  be  impossible  to  detach  the  metal  cast  from  the 
case  when  molded.  The  separation  can  be  readily  effected  by 
substituting  a  metal  shell  for  the  solid  cast.  The  shell  is  formed 
in  the  following  manner  :  Secure  a  perfect  mold  of  the  plaster 
model  in  sand,  and  fill  into  this  with  fused  block  tin  of  the 
purest  kind,  pouring  it  as  hot  as  can  be  poured  without  produc- 
ing bubbling  of  the  metal.  As  the  metal  cools  first  at  the  sur- 
face, a  shell  will  form  externally  in  a  few  seconds,  when  the  box 
containing"  the  mold  should  be  inverted  and  the  central  fluid 
mass  poured  out  quickly  at  the  back  part  of  the  mold  in  prder 
to  secure  the  thinnest  portion  of  the  shell  in  front,  where  it 
should  not  be  thicker  than  ordinary  card  paper.  A  little  prac- 
tice, with  a  few  failures  at  first,  will  enable  the  operator  to  secure 
the  desired  thickness  of  the  shell  with  tolerable  exactness. 
When  obtained,  the  shell  is  filled  in  with  hard-setting  plaster  to 
form  the  metal-faced  model  to  be  used  in  molding  the  celluloid. 
When  the  case  is  finished  and  the  plaster  removed  from  the  shell, 
the  overlapping  borders  of  the  latter  may  be  readily  drawn  in 
toward  the  center  with  pliers,  and  the  shell  disengaged  from  the 
undercut  spaces.  To  facilitate  its  removal,  the  shell,  before  fill- 
ing in  with  plaster,  may  be  divided  vertically  at  intervals  with  a 
fine  saw,  extending  the  cuts  from  the  margins  to  near  the  summit 
of  the  ridge. 

Waxing  or  Modeling. — After  having  arranged  the  teeth  for 
any  given  case,  place  them  with  the  trial  plate  on  the  model,  and 
build  out  with  wax,  paraffin  and  wax,  or  modeling  compound. 
In  carving  or  modeling  these  materials,  much  time  and  labor 
may  be  saved  in  final  finishing  of  the  piece,  and  a  more  compact 
surface  given  to  the  celluloid,  by  securing  in  the  first  place  the 
exact  form  and  fullness  required  in  the  completed  set.  When 
this  is  done  with  instruments  especially  adapted  to  the  purpose, 
the  general  forms  of  which  are  represented  in  Fig.  550,  additional 
smoothness  of  the  surface  may  be  obtained  with  a  blowpipe  flame 
applied  in  such  a  way  as  to  produce  simple  surface  fusion  of  the 
wax  or  other  material.  The  palatal  and  exterior  surfaces  may 
then  be  covered  with  No.  60  tin   foil,  carefully  burnished  into 


CELLULOID    BASE. 


577 


Fig.  550. 


Fig.  551. 


¥■■■' 


J 


J 


close  contact.  A  closer  imitation  of 
the  granular  appearance  of  the  natu- 
ral gum  exteriorly  may  be  obtained 
by  pitting  or  "stippling"  the  surface 
with  a  small  pointed  instrument, 
care  being  taken  not  to  perforate, 
but  simply  indent,  the  foil ;  or  a  flat- 
faced  serrated  plugger  may  be  used 
for  the  same  purpose. 

Investing. — The  piece  prepared 
as  above  is  then  placed  in  a  flask 
especially  designed  for  celluloid 
(see  Fig.  551),  invested  in  plaster, 
and  the  mold  or  matrix  formed  in 
the  same  manner  as  practised  when 
rubber  is  used.  In  case  the  ridge 
overhangs,  oris  undercut,  the  model, 
before  being  encased  in  the  lower 
section  of  the  flask,  should  be  cut 
across  diagonally,  with  the  slope 
toward  the  heel  of  the  model,  thus 
depressing  the  latter  posteriorly,  as 
exhibited  in  Fig.  551.  By  this  means 
the  projecting  portion  of  the  ridge 
will  be  brought  more  directly  in  a 
line  with  the  pressure  in  closing  the 
flask. 

It  is  quite  as  important  that  the 
encasing  plaster  forming  the  matrix 


5/8  MECHANICAL    DENTISTRY. 

should  be  as  hard  and  resistant  to  pressure  as  that  entering 
into  the  composition  of  the  plaster  model.  If  this  condition 
is  not  secured,  there  will  be  great  danger,  not  only  of  fracture 
of  the  model  for  the  want  of  adequate  lateral  support,  but  of 
displacement  of  the  teeth  by  being  forced  into  the  plaster.  So 
important  is  the  right  condition  and  manipulation  of  plaster 
in  the  use  of  celluloid,  that  the  author  feels  warranted  in 
adding,  to  what  has  already  been  said  in  this  connection,  the 
following  judicious  comments  contained  in  a  pamphlet  issued  by 
the  manufacturers  of  celluloid: — 

"  Plaster  should  always  be  mixed  as  tJiick  as  possible,  and,  if 
convenient,  allowed  to  set  overnight,  with  the  flask  open,  and 
dried  in  a  warm  place,  as  it  is  thereby  rendered  much  harder. 
Simple  as  the  operation  is,  comparatively  few  understand  how  to 
mix  plaster  so  as  to  get  the  greatest  strength  and  resistance  to 
pressure.  The  proper  way  to  mix  plaster  for  both  models  and 
filling  flask  is  as  follows  :  First,  stir  the  plaster  as  thick  as  can 
be  well  poured,  taking  care  that  there  is  no  excess  of  water ; 
pour  some  of  this  into  the  flask  or  impression  to  be  filled,  and 
shake  down  well.  Then,  into  what  remains  in  the  bowl,  stir 
more  plaster  until  you  have  a  mass  so  thick  that  it  can  be  piled 
up.  With  this  the  flask  is  filled  up  and  thoroughly  shaken  down. 
It  is  surprising  how  much  plaster  can  be  stirred  in  after  the  first 
is  poured  out,  and  also  how  thick  a  mass,  such  as  described,  will 
settle  down  in  the  flask  without  bubbles.  The  thinner  plaster 
first  poured  in  will  run  and  be  driven,  by  the  thicker  afterward 
added,  into  all  the  crevices,  and  most  of  it  will  escape  from  the 
flask,  leaving  a  body  of  solid,  resisting  plaster  that  cannot  be 
obtained  by  the  ordinary  method  of  mixing." 

In  flasking  the  case,  tJie  line  of  separation  between  the  tipper 
and  loiver  seetions  should  be  along  the  borders  of  the  plate.  This 
is  particularly  necessary  when  the  gum  is  "  stippled."  When 
the  piece  is  incased,  and  the  plaster  has  sufficiently  hardened, 
the  two  sections  of  the  flask  should  be  carefully  separated,  and 
this  can  be  done  with  greater  safety  to  the  model  and  other 
portions  of  the  matrix,  and  with  less  liability  of  loosening  and 
detaching  the  teeth  from  the  plaster,  by  first  applying  just 
sufficient  heat  to  the  flask  to  soften  the  wax  and  trial  plate. 


CELLULOID    BASE.  579 

being  careful  not  to  melt  the  wax  by  too  great  or  long-continued 
heat. 

When  the  flask  is  separated,  all  portions  of  wax  or  other 
material  should  be  carefully  and  thoroughly  removed  from  the 
mold,  and  if  any  remain,  not  accessible  to  instruments,  the  section 
or  sections  of  the  flask  containing  remains  of  wax  should  be 
placed  in  a  clean  vessel  under  clean  water  and  well  boiled  until 
all  is  expelled.  The  thin,  frail  edges  encircling  the  matrix  in 
both  sections  of  the  flask  should  then  be  cut  away  somewhat, 
and  well  rounded  to  prevent  fracture  and  consequent  mixing  of 
particles  of  plaster  with  the  celluloid  in  molding.  When  this  is 
done,  put  the  flask  together  and  see  if  there  is  ample  room  for 
the  "  nose  "  of  the  model  to  pass  the  edge  of  the  matrix. 

To  permit  the  escape  of  surplus  material  in  molding,  either  of 
the  following  plans  maybe  adopted:  i.  Cut  two  concentric 
grooves  in  the  plaster  of  the  upper  or  lower  section  completely 
encircling  the  matrix,  the  inner  one  not  less  than  one-fourth  or 
one-sixth  of  an  inch  from  the  margin  of  the  mold,  and  the  other 
at  the  border  of  the  flask,  the  inner  side  of  the  latter  forming  a 
part  of  the  outer  groove.  2.  Bevel  the  plaster  around  the  mold, 
commencing  about  one-fourth  of  an  inch  from  the  margins  of 
the  latter  and  extending  it  to  the  sides  of  the  flask.  3.  Cut 
cone-shaped  cross  or  radiating  grooves  from  the  inner  circular 
gutter  to  the  margins  of  the  flask, — shallow  where  they  connect 
with  the  circular  groove,  and  deepening  and  widening  toward 
the  edges  of  the  flask. 

In  no  case  should  cross  grooves  be  made  communicating 
with  the  matrix,  as  these  afford  too  ready  an  exit  for  surplus 
material,  and  prevent  that  "  back  pressure  "  so  essential  to  a 
complete  and  compact  filling  of  the  mold.  The  grooves  should 
be  deep  and  ample  enough  to  receive  all  surplus,  otherwise  it 
would  be  difficult,  if  not  impossible,  to  close  the  flask  perfectly. 
In  the  use  of  gum  teeth,  holes  may  be  drilled  in  the  matrix 
inside  the  teeth,  opposite  each  joint,  not  over  an  eighth  of  an 
inch  in  diameter,  and  as  deep  as  it  may  be  deemed  necessary. 
These  act  as  waste  gates,  and  relieve  the  blocks  from  pressure. 

Selection  and  Preparation  of  the  Celluloid  Plate  or  Blank. 
— The  mold  having  been  prepared  in  the  manner  described,  a  - 


580  MECHANICAL    DENTISTRY. 

suitable  blank  should  be  selected,  and,  as  it  is  important  that  this 
should  be,  as  nearly  as  possible,  the  size  and  general  form  of 
the  mold,  a  good  assortment  of  plates,  for  both  entire  and 
partial  pieces,  should  be  at  command  from  which  to  select  for 
any  given  case.  Special  attention  is  directed  to  this  important 
requirement.  Celluloid  does  not,  like  rubber,  flow  together  and 
intimately  intermix  when  exposed  to  heat  and  pressure.  If, 
therefore,  the  blank  is,  in  any  considerable  degree,  wider  than 
the  model,  or  its  central  or  palatal  portion  fuller  and  deeper 
than  that  of  the  model,  the  material,  when  under  pressure,  will 
lap  or  fold  upon  itself  along  the  lateral  walls  of  the  arch,  and, 
failing  to  unite,  will  form  grooves  or  fissures.  On  the  other 
hand,  if  it  is  not  wide  or  deep  enough,  the  material  is  liable  to 
be  stretched  and  torn.  The  blank  should  be  just  large  enough 
to  fill  all  parts  of  the  mold  perfectly,  with  some  slight  excess, 
and  the  central  portion  should  always  be  somewhat  thicker  than 
the  corresponding  part  of  the  trial  or  pattern  plate. 

As  celluloid  cannot  be  depended  on  to  flow  from  one  part  of 
the  mold  to  another,  it  is  important  that  there  should  not  only 
be  an  excess  of  material,  but  that  this  excess  should  be,  as  nearly 
as  practicable,  distributed  throughout  all  portions  of  the  matrix. 
A  neglect  of  this  precaution  will  result  either  in  an  imperfect 
filling  of  the  mold  in  some  places,  and  consequent  defect  of  the 
plate,  or  a  porous  condition  of  the  celluloid  will  be  found  wher- 
ever the  material,  though  apparently  filling  the  mold,  has  not 
been  impacted  with  sufficient  force. 

The  selected  blank  should  be  conformed  as  nearly  as  possible 
to  the  shape  of  the  mold  by  heating  it  in  boiling  water  and 
pressing  it  with  the  fingers  into  the  section  of  the  matrix  con- 
taining the  teeth  ;  after  which  the  necessary  fullness  of  the 
several  parts  of  the  blank  may  be  obtained  by  dressing  away 
redundant  portions  with  files,  a  small  bracket  saw,  or  the  knife, 
first  softening  the  plate  in  boiling  water  before  using  the  latter. 

Greater  exactness  in  the  required  amount  of  celluloid  neces- 
sary in  any  given  case  may  be  obtained  by  measurement,  the 
simplest  method  being  by  the  use  of  the  Starr  instrument, 
illustrated  in  the  chapter  on  Vulcanite.  It  must  be  remem- 
bered, however,  that  this  device  only  determines  the  aggregate 


CELLULOID    BASE.  58  I 

amount  of  material  necessary,  and  that,  while  it  may  be  a  safe 
guide  in  the  use  of  rubber,  which  flows  freely,  it  may  lead  to 
failure  when  celluloid  is  employed,  unless  care  is  taken  that  all 
parts  of  the  blank  correspond  with  the  capacity  of  the  mold. 

A  more  reliable  though  somewhat  tedious  method  of  secur- 
ing exactness  in  the  quantity  and  distribution  of  material  neces- 
sary, and  which  acquires  special  value  in  cases  where  there  is 
unusual  danger  of  fracture  of  the  model  or  teeth,  and  especially 
of  the  latter  when  gum  teeth  are  used  and  these  are  ground 
very  thin,  is  the  following,  given  by  a  correspondent  of  the 
Dental  Cosmos :  "  After  preparing  the  case  ready  to  flask, 
remove  the  teeth  from  the  pattern,  stop  the  pin-holes,  then 
remove  the  pattern  and  carefully  flask  it.  When  the  mold 
is  ready,  remove  all  the  wax  or  material  of  the  pattern ; 
place  the  celluloid  'blank;'  apply  heat,  and  cast  the  same  as  if 
for  final  case.  Remove  the  flask  from  the  heater ;  place  it  in 
the  clamp  and  cool  rapidly.  When  it  is  entirely  cool,  remove 
it  from  the  flask,  and  trim  as  carefully  as  for  final  case  until  the 
blank  is  almost  the  same  as  the  pattern  in  thickness  (it  always 
comes  out  thicker).  Now  you  have  a  blank  with  but  little 
excess; — only  what  the  vacuum  and  pins  displace,  or  slightly 
more,  and  exactly  the  shape  of  the  pattern,  minus  the  teeth. 
Set  up  the  case  again,  being  careful  to  make  the  pattern 
the  same  size ;  flask,  and  when  ready  remove  the  pattern  ;  if 
doubtful  as  to  amount  of  excess,  pare  the  edges  of  the  mold 
slightly,  which  will  be  all  that  is  needed.  Replace  the  blank  ; 
apply  heat,  when  but  moderate  pressure  will  be  found  necessary 
to  bring  the  flask  entirely  together.  If  dry  heat  is  preferred, 
dip  the  edges  of  the  blank  to  come  in  contact  with  the  pins  in 
spirit  of  camphor  for  a  few  minutes  before  casting." 

Before  the  blank  is  placed  in  the  flask  preparatory  to  molding, 
some  provision  should  be  made  against  adhesion  of  the  plaster 
to  the  plate.  This  may  be  done  by  oiling  the  surface  of  the 
model,  or  by  coating  it  and  other  portions  of  the  matrix  with 
either  collodion  or  liquid  silex,  or  by  rubbing  the  surfaces  well 
with  French  chalk  or  powdered  soapstone  ;  or  a  layer  of  tin  foil 
may  be  interposed  between  the  model  and  blank.    The  following 


582  MECHANICAL    DENTISTRY. 

novel  method  of  coating  the  surface  of  the  model  with  tin  is 
recommended  by  Charles  P.  Alker,  of  Bordeaux,  France : 
"  Reduce  ordinary  collodion  with  about  three  times  its  bulk  of 
ether,  and  add  powdered  tin  until  the  solution  is  well  impreg- 
nated with  the  metal.  The  tin  is  the  same  that  is  sometimes 
used  for  coating  plaster  images.  When  properly  mixed  and 
applied  with  a  brush,  an  even  covering  of  tin  is  formed  upon  the 
model,  so  dense  as  to  closely  resemble  tin  foil,  and  so  firm  as  to 
not  be  detached  by  boiling  water  or  heat.  The  plate  is  readily 
cleansed  with  a  coarse  brush,  and  presents  the  appearance  of 
having  been  made  in  a  metallic  mold." 

More  perfect  results,  however,  it  is  believed,  can  be  obtained 
in  the  use  of  a  metal-faced  model  in  connection  with  the  use  of 
tin  foil,  as  before  described.  A  piece  thus  encased  in  metal  will 
require  no  more- final  finishing  than  is  necessary  to  remove  sur- 
plus material  and  dress  and  polish  edges. 

The  case,  thus  described,  is  now  ready  for  molding. 

Molding. — The  various  machines  or  heaters  now  generally 
employed  in  molding  celluloid  into  dental  plates  contemplate  the 
use  of  either  glycerin  or  oil,  steam  or  dry  heat,  for  the  purpose 
of  producing  the  requisite  plasticity  of  the  material  subjected  to 
pressure.  There  is  considerable  diversity  in  the  form  and  con- 
struction of  heaters  designed  to  utilize  these  several  mediums 
for  the  conduction  of  heat,  as  well  as  differences  in  the  modes 
of  applying  pressure,  and  while  each  has,  doubtless,  some  special 
points  of  merit  not  possessed  by  others,  satisfactory  results  may, 
with  careful  and  intelligent  manipulation,  be  attained  by  the  use 
of  any  one  of  the  many  recommended.  The  limits  of  this  work 
will  only  permit  the  introduction  of  such  as  are  believed  to  be  in 
most  general  use. 

Hot  Moist  Air  (so-called  "Dry-Heat")  Machines. — In 
the  use  of  these  heaters,  the  water  with  which  the  plaster  is 
impregnated  is  relied  upon  to  produce  the  steam  necessary  to 
carry  off  all  excess  of  camphor  from  the  celluloid  in  the  process 
of  molding.  An  essential  point  by  this  method  is  to  have  the 
plaster  in  the  flask  thoroughly  wet,  and  this  may  be  better 
attained  by  setting  the  flask  in  a  vessel  of  water  before  placing  it 


CELLULOID    BASE. 


583 


in  the  heater.  To  provide  against  insufficiency  of  moisture  in 
the  plaster,  a  small  quantity  of  water  may  be  introduced  into  the 
tank  before  applying  heat. 

Fife-  552  represents  a  modeling  or  packing  machine  of  the 
class  here  spoken  of,  and  is  designated  as  the  "Best."  The 
inside  chamber  is  of  cast-iron,  surrounded  by  a  sheet-iron 
casing.  The  lid,  of  cast-iron,  forming  a  part  of  the  clamp,  is 
pierced  for  the  passage  of  three  wrought-iron  screw-bolts, — the 
nuts  being  on  the  upper  side  and  easy  of  access.     When  these 


nuts  are  turned  for  the  purpose  of  closing  the  clamp,  the  bottom 
portion  of  the  clamp  is  drawn  up  by  each  revolution  away  from 
the  flame,  thus  avoiding  the  danger  of  overheating  the  plate,  and 
securing  a  uniform  heat.  The  bottom  of  the  cast-iron  chamber 
and  the  lid  are  pierced  with  holes,  to  allow  a  circulation  through 
the  chamber,  for  the  purpose  of  carrying  off  the  camphor  which 
is  disengaged  in  the  process. 

With  the  celluloid  blank  adjusted  to  its  proper  position  in  the 
flask,  the  latter  is  placed  in  the  clamp  and  the  top  screwed  down 


584  MECHANICAL    DENTISTRY. 

until  it  slightly  presses  the  clamp.  It  is  then  placed  in  the  oven 
or  tank  and  heat  applied. 

If  gas  is  used,  the  form  of  burner  shown  underneath  the 
heater  in  Fig.  552,  which  gives  a  pure  blue  flame  without  smoke, 
may  be  used.  If  gas  cannot  be  commanded,  however,  any  of 
the  alcohol  or  kerosene  lamps  commonly  employed  in  vulcan- 
izing may  be  substituted;  or  the  "  Hot  Blast  Oil  Stove,"  espe- 
cially adapted  to  the  "  Best  "  machine,  and  exhibited  in  connec- 
tion with  the  latter  in  Fig.  553,  and  its  construction  in  detail 
shown  in  sectional  diagram,  Fig.  554,  will  be  found  convenient 
and  efficient. 

Having  applied  tire  heat,  it  is  of  the  first  importance  that 
unremitting  attention  should  be  given  to  the  process  of  molding 
until  it  is  completed.  If  pressure  is  applied  before  the  celluloid 
is  rendered  somewhat  plastic,  or  too  great  force  is  exerted  during 
the  earher  stages  of  the  process,  and  without  sufficient  intervals 
of  rest,  there  is  danger  of  crushing  or  fracturing  the  model  and 
of  impairing  the  articulation  by  displacement  of  the  teeth.  On 
the  other  hand,  the  nature  of  celluloid  is  such  that  if  it  is 
exposed  to  a  temperature  of  270°,  without  being  under  pressure, 
the  camphor  evaporates,  and  the  material,  besides  being  rendered 
hard  and  intractable,  is  puffed  up,  exactly  as  a  loaf  of  bread  is 
raised  by  yeast,  and  filled  with  air  cells,  and  thus  rendered 
porous. 

Celluloid  begins  to  soften  at  about  225°,  and  will  then  yield 
slightly  to  pressure,  but  this  should  be  applied  very  gently  at  first, 
with  no  more  force  than  can  be  readily  exerted  with  the  thumb 
and  finger.  As  the  heat  increases,  and  the  celluloid  becomes 
more  and  more  plastic  and  yielding,  the  pressure  should  be  corre- 
spondingly increased,  but  always  interruptedly,  giving  the 
material  time,  between  each  turn  of  the  screw  or  nuts,  to  escape 
from  under  the  pressure.  No  considerable  amount  of  pressure 
will  be  required  in  any  case  until  near  the  close  of  the  operation, 
when  the  mold  is  completely  impacted,  and  the  excess  is  being 
forced  into  the  grooves  or  gateways  as  the  flask  comes  together- 

At  this  point  considerable  force  will  be  necessary  to  close  the 
flask  perfectly,  and  somewhat  longer  intervals  of  time  should 
occur  between  each  turn  of  the  screw  or  nuts. 


CELLULOID    BASE. 


585 


During  the  progress  of  the  molding,  the  flask  should  be 
withdrawn  occasionally  for  inspection.  If,  in  the  case  of  central 
pressure,  the  flask  is  found  to  be  closing  unevenly,  it  should  be 
loosened  in  the  clamp  and  readjusted  in  such  manner  as  to 
correct  the  faulty  approximation.  No  difficulty  will  be  experi- 
enced in  this  respect  in  the  use  of  clamps  provided  with  screw- 
bolts,  as  pressure  may  be  applied  at  any  point,  and  the  flask  be 
'made  to  close  uniformly  without  the  necessity  of  shifting  the 
latter. 

Fig.  553.  Fig.  554. 


A.  Reservoir,  made  of  galvanized  iron.  B. 
Top  of  reservoir.  C.  Cliimneys.  D. 
Drum.  E.  Hanging  partition,  which  keeps 
the  radiated  heat  from  reservoir.  F. 
Principal  air  deflectors.  H.  Supple- 
mentary air  deflectors.  T.  Tank  sur- 
rounding wick  tube.  R.  Perforated  ring 
through  which  all    the  air  that  supplies 

•  the  stove  passes.  W.  Wick  chamber. 
X.  Wick  tubes. 


The  moment  the  flask  is  completely  closed,  the  heat  should 
be  turned  oft",  and  the  piece  allowed  to  cool  gradually.  In  no 
instance  should  the  flask  be  removed  from  the  clamp  (unless 
securely  locked,  as  is  practicable  with  the  "  standard  "  flask)* 
until  it  is  stone  cold.  In  cases  where  the  material  is  of  extra 
thickness,  or  where  the  shape  of  the  blank  is  totally  altered, 
longer  seasoning  is  advisable,  and  the  flask  should  be  placed 
near  a  stove  or   over  a   register  (keeping   it  closed  by  a  clamp. 


*  Manufactured  by  the  Celluloid  Company,  and  represented  in  Fig.  555. 


586 


MECHANICAL    DENTISTRY. 


or  by  an  instrument  or  piece  of  iron  put  through  the  holes  in  the 
standard)  for  half  a  day  or  more,  at  a  temperature  not  over  140°. 
If  these  directions  are  observed,  no  trouble  from  warping  plates 
will  be  experienced. 

Molding  in  Glycerin. — Glycerin,  as  a  medium  of  imparting 
heat  in  the  process  of  molding  celluloid,  has  almost  entirely 
superseded  the  use  of  oil,  paraffin,  and  other  allied  substances 
originally  employed.  It  is  a  favorite  method  with  many  practi- 
tioners, and  is  recommended  by  the  manufacturers  of  celluloid 

Fig.  555. 


as  superior  to  any  other.  The  long  and  familiar  acquaintance  of 
these  parties  with  the  composition,  nature,  behavior,  and  treat- 
ment of  the  material  they  produce  entitles  their  opinion  and 
preferences  to  more  than  ordinary  consideration. 

The  improved  glycerin  apparatus  manufactured  by  them  is 
exhibited  in  Fig.  555,  consisting  of  a  tank.  A,  for  containing 
the  glycerin  ;  a  stand,  S,  with  detachable  legs,  L,  which  slip 
into  slots,  as  shown  at  S  ;  an  alcohol  cup,  shown  at  K  in 
sectional  diagram  of  steam  machine.  Fig.  556;  a  screw  clamp, 
B  ;  a  flask,  C  ;  and  a  thermometer,  D,  to  indicate  the  heat. 


CELLULOID    BASE. 


587 


Either  alcohol  or  gas  may  be  used  with  this  machine.  When 
kerosene  is  employed,  the  manufacturers  recommend  the  use  of 
the  "  leader "  oil  stove.  When  this  stove  is  used,  the  long 
legs  of  the  steam  machine  must  be  substituted  for  the  shorter 
ones  represented  in  Fig.  555. 

Fig.  556. 


M  and  N,  in  the  sectional  drawing,   represent    packing,  to  make  the    boiler 

steam-light. 


Having  placed  the  blank  in  the  flask,  put  the  latter  into  the 
screw  clamp  and  turn  down  the  screw  until  it  touches  the  flask 
lightly  ;  set  the  whole  into  the  tank  and  pour  enough  glycerin 
into  the  latter  to  come  up  to  about  the  top  of  the  flask.  Apply 
heat,  and   proceed    with  the  molding    in  the  same  manner  as 


588  MECHANICAL    DENTISTRY, 

described  in  connection  with  the  "  moist  air  "  method.  The  heat 
should  not  be  permitted  to  rise  much  above  280°.  If  the  flask 
is  not  closed  when  that  temperature  is  reached,  reduce  the  flame, 
and  do  not  hasten  the  closing.  A  little  practice  will  enable  the 
operator  to  graduate  the  pressure  exactly,  without  reference  to 
the  thermometer. 

Molding  in  Steam. — A  sectional  diagram  of  the  best  adapted 
apparatus  where  steam  is  used  in  molding  is  shown  in  Fig.  556. 
It  consists  of  the  following  parts  :  The  base,  or  standard,  J 
(now  made  with  detachable  legs,  as  in  cut  of  glycerin  machine); 
the  boiler,  B  ;  the  cover,  D,  to  which  is  attached  the  safety  valve, 
H  ;  the  plunger,  E,  and  alcohol  cup,  K  ;  the  screw,  F,  for  closing 
the  flask,  operated  by  the  handle,  L;  the  gland  or  packing  ring, 
G,  the  object  of  which  is  simply  to  prevent  the  steam  from  leak- 
ing around  the  screw ;  and  the  wrench  or  spanner. 

The  stand  is  the  same  as  that  for  the  glycerin  machine 
shown  in  Fig.  555,  and  is  furnished  with  short  legs,  as  shown 
in  that  cut  (for  alcohol  or  gas),  or  long  legs  as  above,  as  desired. 
To  use  the  old  steam  machine  with  the  "Leader"  stove,  it  is 
necessary  to  order  only  the  improved  stand  with  long  legs. 
The  company  always  send  the  short  legs  unless  otherwise 
ordered.     The  following  are  the  directions  given : — 

"  In  using  the  steam  machine,  care  should  be  taken  to  keep  it 
in  good  order.  The  screw  should  be  well  oiled  with  only  the 
best  sperm  oil,  which  will  not  gum,  and  kept  so  that  it  can  be 
easily  turned  with  the  thumb  and  finger.  If  the  machine,  when 
received  from  the  depot,  works  hard,  the  screw  should  be  rua 
out,  the  gland  unscrewed,  and  the  rubber  packing  loosened  up, 
so  that  it  will  not  bind  the  screw.  Do  not  turn  it  down  tight 
again  until  you  heat  it  up,  when,  if  it  begins  to  leak,  it  can  easily 
be  tightened.  Bear  in  mind  that  tnr/iiiig  this  gland  merely  pre- 
vents the  escape  of  steam,  and  does  not  affect  the  pressure  on  the 
flask. 

"  The  safety-valve  should  be  kept  free  from  gum,  and  if  either 
it  or  the  screw  is  clogged,  it  should  be  well  cleansed  with  kero- 
sene. This  valve,  in  the  machine  now  sold,  is  so  constructed 
that  it  blows  off  at  about  275°,  a  temperature  that  celluloid  will 
bear  very  well ;  and  as  the  heat,  so  long  as  zvater  remains  in  the 


CELLULOID    BASE.  589 

boiler,  cannot,  if  the  safety-valve  is  kept  in  order,  be  raised  above 
that  point,  it  is  impossible  to  burn  a  plate  in  this  machine 
While  this  is  true,  it  is  also  true  that  too  long  an  exposure  to 
even  275°  in  steam  tends  to  injure  the  quality  of  the  celluloid, 
and  for  this  reason  the  heat  should  be  continued  no  longer  than 
necessary,  but  should  be  reduced  at  once  by  blowing  off  steam 
as  soon  as  the  molding  is  completed.  The  first  machines  were 
constructed  v/ith  the  safety-valve  much  heavier,  and  all  in  one 
piece,  and  were  adjusted  to  a  temperature  of  nearly  300°,  which 
was  higher  than  necessary  or  advisable.  It  is  recommended, 
therefore,  that  those  having  that  style  of  valve  should  cut  off 
about  one-fourth  in  weight  from  the  lead  weight,  which  can 
easily  be  done  by  removing  a  little  wire  which  passes  through 
the  stem  and  weight.  A  modern  valve  will  be  furnished  when 
ordered.  When  molding,  fill  the  boiler  partly  full  of  water. 
The  amount  is  not  material,  but  there  should  always  be  enough 
to  cover  the  ribs  at  the  bottom.  Have  the  screw  well  turned 
back,  until  the  plunger,  when  placed  in  position,  will  rest  against 
the  top  of  the  boiler,  otherwise  the  flask  may  be  pressed  upon 
while  screwing  dowh  the  cover  and  the  cast  injured.  Turn  down 
the  cover  snugly;  see  that  the  gland  is  turned  back,  and  the 
screw  works  freely.  Many  failures  have  occurred  by  neglecting 
this  simple  matter.  If  it  works  hard,  it  is  impossible  to  tell 
how  much  or  how  little  pressure  is  being  exerted  ;  there  may  be 
too  much,  and  blocks  or  cast  be  broken  ;  or  too  little,  and  the 
plate  made  porous.  In  all  methods  of  working  celluloid,  the 
sense  of  feeling  is  the  best  guide  as  to  when  and  how  hard  to 
turn  ;  but  in  order  to  have  this,  there  must  be  perfect  freedom  of 
motion  of  the  parts.  The  time  elapsing  before  turning  is  not 
reliable,  as  it  varies  with  the  heat  employed,  the  temperature  at 
starting,  the  amount  of  water  in  the  boiler,  the  drafts  of  air  to 
which  the  flame  may  be  subjected,  etc. 

"After  placing  the  flasks  in  position,  turn  down  the  screw 
very  gently,  with  thumb  and  finger,  until  you  feel  it  touch  the 
flask.  Fill  the  cup  with  alcohol  and  light  it,  or  light  the  gas. 
The  safety-valve  is  made  in  two  parts.  The  upper  portion  may 
be  suspended  by  the  pins  in  the  lead  weight ;  the  valve  will  now 
blow  off  steam  (if  in  proper  order)  at  a  temperature  of  225°. 


590  MECHANICAL    DENTISTRY. 

Until  this  occurs,  no  particular  attention  is  necessary,  but  from 
that  time  the  exclusive  attention  of  the  operator  should  be  given 
to  the  molding.  Many  failures  occur  from  the  want  of  this,  for 
the  plate  may  be  easily  injured  from  too  much  heat  without 
proper  pressure.  But  fifteen  or  twenty  minutes,  at  the  most,  will 
be  required  from  this  point,  with  proper  heat,  and  nothing  else 
should  be  attended  to. 

"  At  the  point  when  the  steam  escapes  from  the  valve  with  the 
upper  portion  suspended,  the  plate  will  soften,  and  the  screw  will 
be  felt  to  yield  to  light  pressure  with  thumb  and  finger.  The 
upper  weight  should  now  be  dropped  down.  Turn  the  screw 
vay  carefully,  stopping  when  you  feel  the  resistance  increase; 
as  soon  as  it  yields  again,  turn  it  more,  going  slowly  and  care- 
fully at  first,  but  increasing  the  pressure  somewhat  as  the  steam 
gets  up,  which  you  will  know  by  occasionally  raising  the  valve. 
It  is  just  here  that  judgment  is  required  to  avoid,  on  the  one 
hand,  too  much  pressure  before  the  material  is  sufficiently  soft- 
ened, which  would  result  in  fracture  of  the  cast  or  blocks,  disar- 
ranging the  articulation,  or  a  '  flaky'  plate;  and,  on  the  other, 
too  little  pressure  after  the  heat  is  up,  which  would  result  in 
injuring  the  quality  of  the  material.  The  pressure  should  be 
followed  up  as  the  heat  rises  and  the  screw  yields,  the  object 
being  to  get  the  whole  of  the  plate  under  pressure,  in  every  part 
of  the  mold,  by  the  time  the  steam  blows  off  quite  sharply  and 
steadily  on  raising  the  safety-valve.  After  this  the  pressure 
should  be  increased,  but  time  should  always  be  given  between 
the  turns  for  the  slowly  flowing  celluloid  to  escape  from  under 
the  pressure.  Toward  the  close  of  the  process,  the  pressure 
should  be  considerable  ;  in  fact,  about  all  that  can  be  applied 
with  the  machine,  and  should  be  continued  as  long  as  the  screw 
can  be  turned.  If  the  operation  has  been  properly  timed,  the 
steam  will  blow  off  at  the  safety-valve  at  about  the  time  the 
molding  is  completed  and  the  alcohol  in  the  cup  is  consumed. 
If  it  should  blow  off  before  that,  no  harm  would  be  done,  as  the 
heat  cannot  become  too  great  if  the  safety-valve  is  kept  in  proper 
condition.  These  remarks  apply  to  the  use  of  alcohol  in  the  cup 
furnished  with  the  machine.  If  any  other  heat  is  used,  the  flame 
should  be  sufficient  to  complete  the  process  within  thirty  to  forty 


CELLULOID    BASE.  59I 

minutes.  If  more  than  this  time  is  consumed  in  the  molding", 
the  quality  of  the  plate  is  injured. 

"  Do  not  allow  the  water  to  be  all  converted  into  steam,  as  the 
steam  would  then  become  superheated,  and  a  dangerous  condi- 
tion ensue  or  the  plate  be  ruined,  while  the  safety-valve  would 
not  indicate  it.  Always  have  plenty  of  water  in  the  boiler,  and 
if  steam  should  cease  to  issue  on  raising  the  valve,  the  heat 
should  be  at  once  withdrawn." 

It  has  been  demonstrated  by  experimental  tests,  and  is  now 
very  generally  conceded,  that  the  best  results  are  obtained  in  the 
use  of  celluloid  by  subjecting  it  to  dry  heat  in  the  process  of 
molding,  the  material,  when  exposed  to  a  high  temperature 
under  such  a  condition,  retaining  most  perfectly  its  form,  color, 
and  consistency.  Hence  the  celluloid  presses  of  more  recent 
introduction,  while  they  are  also  ecjually  well  adapted  to  vulcan- 
izing by  the  same  means,  are  provided  with  a  distinct  chamber 
in  which  hot  air,  of  a  higher  temperature  than  can  be  safely  em- 
ployed with  glycerin  or  steam,  is  utilized  to  secure  the  greatest 
practicable  plasticity  of  the  celluloid.  Approved  appliances  of 
this  kind  are  those  devised  by  Drs.  Seabury,  Evans,  and  Camp- 
bell. The  former  ,two  have  already  been  described  in  the  pre- 
vious chapter. 

The  New  Mode  Heater. — Dr.  Carnpbell's  apparatus,  famil- 
iarly known  as  the  "New  Mode  Heater,"  exhibited  in  Fig.  557, 
is  constructed  as  follows  :  The  apparatus,  designed  alike  for  vul- 
canizing and  molding  celluloid,  used  more  generally,  perhaps,  for 
the  latter  purpose,  consists  of  a  cylindrical  cast  vessel,  having  two 
chambers,  one  within  the  other,  the  inner  one  being  supported  by 
piers  or  columns  connecting  its  sides,  top,  and  bottom  with  those 
of  the  outer  chamber,  the  whole  being  made  in  one  casting.  The 
outer  compartment  is  the  steam  chamber  or  boiler,  and  encloses 
the  hot-air  or  packing  chamber  on  all  sides,  except  the  front, 
where  the  walls  of  the  two  chambers  converge  and  become  one, 
for  the  purpose  of  permitting  access  to  the  packing  chamber. 
A  door  made  of  the  same  metal  as  the  boiler,  and  fitted  with  lead 
packing,  to  make  it  steam  tight,  is  held  in  place  by  a  bridge 
secured  with  screws.  The  door  is  also  provided  with  a  plate- 
glass  light  (shown  in  cut),  through  which  the  operator  can  watch 


592 


MECHANICAL    DENTISTRY. 


the  progress  of  the  molding  in  the  oven.  The  only  communica- 
tion between  the  chambers  is  by  means  of  a  valve  having  its  seat 
in  the  top  of  the  packing  chamber,  and  controlled  by  a  hollow 
stem  which  passes  through  the  top  of  the  machine. 

Fig.  557. 


B  is  a  mercury  bath  ;  C,  thermometer  ;  D,  screw  plug  ;  E. 
lam-nut;  F,  stem  of  steam  valve;  G,  screw  cap;  H,  large  screw 
for  closing  flask  ;  I,  I,  I,  smaller  screws  for  same  purpose;  K, 
K,  K,  L,  nickel-plated  caps  for  screws  ;  O,  O,  steam  chamber. 


CELLULOID    BASE.  593 

The  packing  chamber  is  heated  by  steam  generated  in  the 
outer  compartment,  which  is  kept  filled  with  water  on  a  level  with 
the  top  of  the  oven.  The  water  is  introduced  through  an  open- 
ing in  the  top  and  side  of  the  boiler,  into  which  the  thermometer 
is  screwed,  and  which  may  be  removed  for  the  purpose.  Steam 
may  be  introduced  from  the  boiler  into  the  packing  chamber  by 
partly  unscrewing  the  lam-nut,  E,  or  wholly  excluded  by  tight- 
ening the  same.  With  this  arrangement,  an  absolutely  dry 
packing  oven  is  possible  in  molding.  The  following  directions 
in  the  use  of  this  heater  are  given  by  the  inventor: — 

"  To  secure  the  best  practical  results,  celluloid  should  be 
molded  or  pressed  into  the  form  desired  at  the  highest  possible 
temperature  which  will  not  burn  it.  To  prove  this,  it  is  only 
necessary  to  mold  a  plate  on  a  metal  cast  at  the  lowest  tempera- 
ture at  which  it  can  be  done,  which  is  less  than  212°,  and  an- 
other on  the  same  cast  at  the  highest  temperature  possible,  say 
310°  or  320°,  and  lay  the  two  aside  for  a  few  days,  when  it  will 
be  found  that  the  one  molded  at  the  lower  temperature  will  not 
fit  the  cast,  while  that  molded  at  the  higher  temperature  will  fit 
as  well  as  when  first  made.  The  reason  is  that  the  low  tempera- 
ture fails  to  overcome  the  tendency  of  the  plate  to  return  to  its 
original  form,  while  the  high  temperature  renders  it  so  thor- 
oughly plastic  that  this  tendency  is  entirely  eradicated.  This  is 
proportionally  the  case  with  pieces  made  at  intermediate  tem- 
peratures ;  the  higher  the  temperature  to  which  the  plate  is  sub- 
jected in  molding,  the  more  exactly  will  it  hold  its  new  form  and 
the  less  will  be  its  tendency  to  warp. 

"  Celluloid  may  be  readily  and  safely  manipulated  in  the  New 
Mode  Heater  at  320°,  a  temperature  many  degrees  higher  than  is 
deemed  safe  in  other  machines,  and  which  accomplishes  per- 
fectly the  result  above  noted,  and  produces  a  plate  which  is  be- 
lieved to  be  absolutely  unchangeable  in  color,  form  and  texture. 
When  this  very  high  temperature  is  employed,  the  celluloid 
should  be  in  the  machine  only  long  enough  to  permit  the  closing 
of  the  flask,  for  the  reason  that  heat  vaporizes  the  camphor — 
the  solvent  of  the  material.  If  too  much  of  this  is  driven  off 
before  the  flask  is  closed,  it  will  be  almost  impossible  to  mold 
the  blank  to  the  desired  form.     The  sooner  the  flask  is  closed 


594 


MECHANICAL    DENTISTRY. 


after  being  placed  in  the  oven,  the  more  readily  will  it  be  done, 
and  the  better  will  be  the  result. 

"  The  molded  surface  of  a  piece  of  celluloid  is  much  more 
durable  than  its  interior,  and  will  retain  the  color  better.  It  is 
obvious,  therefore,  that  this  surface  is  essential  to  the  integrity 
of  the  plate,  and  should  be  preserved  intact.  To  insure  this, 
the  case  should  be  so  prepared  that  the  plate,  when  taken  from 
the  flask,  will  require  little  or  no  labor  to  make  it  ready  for  use. 
It  is  possible  that  some  surplus  material  at  the  edges  may  have 
to  be  trimmed  off  and  the  edges  smoothed,  but  the  case  is  not 
properly  prepared  if  more  than  this  is  necessary.  The  care  and 
trouble  involved  in  proper  preparation  will  really  save  time,  will 
absolutely  avoid  interference  with  the  fit  by  the  too  free  use  of 
files,  sand  paper,  pumice,  etc.,  and  will  insure  a  durable  plate 
with  a  permanent  imitation  of  gum  color.  Moreover,  the  artis- 
tic taste  of  the  operator  may  be  exercised  before  the  plate  is 
molded  more  readily  than  afterward. 

"  Paraffin  and  wax  compound  is  used  for  the  base-plate,  ac- 
cording to  directions  before  given,  and  the  teeth  arranged,  the 
wax  carved  into  the  shape  desired  by  means  of  carving  tools, 
and  made  smooth.  The  piece  is  then  invested  in  plaster,  the 
usual  grooves  cut,  the  wax,  teeth  and  tin  foil  being  removed 
with  the  upper  half  of  the  flask  in  parting.  The  wax  is  then 
removed  by  means  of  boiling  water,  as  before  described,  the  tin 
foil.  No.  60,  used  for  covering  the  paraffin  and  wax  plate,  re- 
maining upon  the  plaster ;  the  investment  is  now  ready  to  be 
dried  out  preparatory  to  receiving  the  celluloid. 

"  Drying  the  Cast  and  Investment. — To  dry  a  plaster  cast 
and  investment,  and  keep  them  free  from  cracks  and  checks,  is 
very  difficult  by  the  ordinary  means,  but  with  the  New  Mode 
Heater  it  can  be  done  so  perfectly  as  to  permit  their  use  in  cast- 
ing pure  gold  or  gold  alloys. 

"  There  are  two  ways  of  drying  the  investment  in  the  New 
Mode  Heater;  first,  by  raising  the  temperature  to  320°,  keeping 
the  hot  box  dry  ;  second,  by  admitting  steam  to  the  hot  box. 
The  former  method  can  be  used  when  the  investment  is  placed  in 
the  chamber  before  getting  up  steam.  If  steam  is  up,  however, 
either  method  may  be  employed.     In  using  the  dry-heat  method, 


CELLULOID    BASE.  595 

open  very  slightly  the  screw  cap  of  the  piston  or  valve-stem,  to 
permit  the  escape  of  the  steam  generated  from  the  water  in  the 
plaster,  being  careful  that  the  steam-valve  is  firmly  seated,  as 
otherwise  all  the  steam  made  in  the  boiler  will  escape.  In  using 
steam  for  drying,  admit  the  live  steam  into  the  chamber  with  the 
investment,  by  raising  the  valve  from  its  seat,  keeping  the  screw 
cap  closed.  The  steam  quickly  permeates  the  plaster,  and  in 
five  or  ten  minutes  the  temperature  of  the  plaster  is  high  enough 
to  convert  the  water  in  it  into  steam.  As  soon  as  the  plaster  is 
thoroughly  heated,  shut  off  the  steam  by  closing  the  valve, 
and  raise  the  screw  cap  very  slightly,  to  allow  that  in  the 
chamber  to  escape  slowly  through  the  small  aperture  at  the  side 
of  the  screw.  In  a  few  moments  the  cast  will  be  perfectly  dry, 
the  steam  escaping  from  the  chamber,  carrying  with  it  that  gen- 
erated from  the  moisture  in  the  plaster.  Extreme  care  should 
be  taken  that  the  steam  shall  escape  I'ay  slcnvly,  as  otherwise  the 
plaster  may  be  blown  out  of  the  flask  into  the  oven  by  the  too 
rapid  expansion  of  its  vaporized  moisture.  The  completion  ot 
the  drying  process  is.  known  by  steam  ceasing  to  be  given  off  at 
the  screw-cap,  G.  The  drying  may  be  facilitated  by  placing  a 
small  chip  of  wood  between  the  two  parts  of  the  flask  when  it 
is  put  into  the  chamber,  thus  exposing  a  larger  surface  to  the 
heat  and  allowing  the  moisture  to  escape  readily. 

"  Molding  by  Dry  Heat. — When  the  investment  is  dried,  re- 
move it  from  the  chamber,  insert  and  carefully  adjust  the 
selected  blank  ;  replace  the  flask  in  the  oven  immediately  under 
the  screws  ;  see  that  the  two  sections  are  so  placed  that  the 
guide-pins  will  enter  properly  into  the  lugs  ;  open  the  screw-cap 
a  turn  or  two  to  allow  the  escape  of  the  gas  from  the  hot  box ; 
turn  down  the  large  screw  until  it  bears  lightly  upon  the  top  of 
the  flask,  and  close  the  machine.  In  less  than  five  minutes  the 
material  will  be  sufficiently  softened  to  permit  the  commence- 
ment of  the  molding.  The  screws  will  turn  readily  with  the 
thumb  and  finger  (using  the  smaller  key-wrench),  when  the 
blank  is  properly  softened.  Close  the  flask  gradually,  stopping 
occasionally  if  the  resistance  is  too  great.  Usually,  if  the  tem- 
perature is  about  300°,  the  flask  can  be  closed  in  ten  minutes; 
but  if  a  very  thick  blank  is  used,  the   molding   must   proceed 


596  MECHANICAL    DENTISTRY. 

slowly ;  the  small  screws  may  be  used  to  advantage,  and  more 
time,  say  thirty  minutes,  may  be  consumed.  As  soon  as  the 
flask  is  closed — unless  a  lock  flask  is  used — the  flame  should  be 
extinguished,  the  door  opened,  and  the  machine  allowed  to  cool. 
If  a  lock  flask  is  used,  it  may  be  removed  and  thoroughly 
cooled  before  opening  it,  the  oven  being  meanwhile  ready  for 
another  case.  The  cooling  may  be  accomplished  rapidly,  if  ne- 
cessary, by  placing  the  flask  in  water.  When  perfectly  cold, 
remove  the  plate  from  the  investment;  it  will  be  found  enveloped 
in  the  tin  foil  which  had  been  burnished  to  the  wax  plate.  Peel 
off  the  foil.  The  celluloid  will  present  a  hard,  brightly-polished 
surface,  received  from  its  contact  with  the  foil,  and  will  need  no 
further  finishing  than  cutting  off  the  excess  of  material  and 
smoothing  down  the  edges." 

In  the  use  of  material,  as  a  base  for  dentures,  possessing  prop- 
erties so  extremely  sensitive  to  heat  as  that  of  celluloid,  and  so 
liable  to  suffer  changes  of  color  and  structure  materially  affecting 
its  usefulness  by  a  misapplication  of  heat  and  faulty  manipulation, 
everything  that  contributes  to  a  better  understanding  of  its  be- 
havior in  the  process  of  molding  must  be  of  interest  and  prac- 
tical value.  The  following  experiments  of  Dr.  J.  Stewart  Spence, 
of  San  Francisco,  Cal.,  throw  some  additional  light  upon  the 
subject.     He  says:  — 

"  Having  just  made  more  than  thirty  experiments  with  cellu- 
loid and  the  New  Mode  Heater,  I  have  met  with  some  interest- 
ing facts,  of  which,  during  two  years'  previous  use  of  the  appara- 
tus, I  was  ignorant.  The  main  results  I  will  now  give  before 
relating  the  experiments,  thus  inverting  the  usual  order  of  plac- 
ing results  last,  for  the  sake  of  perspicuity. 

"  I.  Plaster  investments  require  one  and  a  half  hours  to  dry 
in  the  oven  of  the  heater,  with  the  thermometer  at  400°,  and 
half  an  hour  more  to  raise  their  heat  to  320°.  Drying  them 
over  a  gas-burner  takes  nearly  as  long,  and  loosens  the  plaster 
from  the  flask.  A  thermometer  placed  between  the  slightly 
separated  halves  of  the  flask  in  the  oven  indicates  when  this 
heat  is  reached,  at  which  time  a  blank,  previously  prepared, 
should  be  expeditiously  inserted. 

"  2.  Celluloid  may  be  molded  in  from   five  to   ten  minutes  at 


CELLULOID    BASE.  597 

320°  ;  in  about  twenty  to  twenty-five  minutes  it  degenerates, 
becoming  brown,  hard,  brittle  and  porous,  and  in  twenty-five  to 
thirty  minutes  it  burns  up. 

"  3.  Celluloid  will  burn  at  either  high  or  low  temperatures, 
according  to  the  length  of  time  it  is  exposed  to  them,  as  well  as 
their  degree  of  heat.  Thus  it  is  unsafe  to  leave  it  at  even  a  low 
heat  for  a  long  time,  as  in  slow  cooling. 

"  4.  Celluloid  is  more  liable  to  spoil  if  not  under  pressure,  and 
those  parts  of  the  blank  least  subject  to  pressure  are  most  liable 
to  come  out  damaged.  Therefore  flasks  should  be  closed  with 
all  expedition. 

"  5.  Celluloid,  unless  worked  at  a  high  temperature,  so  as  to 
flow  readily,  and  with  well-hardened  plaster,  will  press  the  model 
out  of  shape  and  teeth  out  of  position. 

"6.  Steam  brought  in  contact  with  heated  celluloid  makes  it 
puff  up  and  degenerate. 

"  7.  Plaster  retains  heat  longer  than  metal,  and  therefore  plates 
left  in  the  oven  to  cool  may  spoil  or  burn  up  even  when  the  tem- 
perature of  the  heater  has  fallen  to  a  low  degree. 

"  8.  Tin  foil  discolors  celluloid  at  a  high  heat,  making  it 
browner. 

"  9.  Celluloid  after   molding  is  hardest  at  the  surface,  as  may" 
be  clearly  seen  in  a  plate  that  has   been  slightly  overheated,  it 
being  porous  internally,  but  very  hard  on  its  surface. 

"  Instead  of  giving  a  copy  of  my  record  of  these  experiments, 
which  W'ould  be  unnecessarily  prolix,  I  will  give  a  condensed 
account  of  them  by  series. 

"  1st  Series.  To  test  the  heat  of  the  oven.  I  placed  in  the  dry 
oven  a  separate  thermometer,  which,  with  the  door  closed,  regis- 
tered the  same  as  that  outside  ;  then  reversed  them  with  similar 
results.  Removing  the  central  screw  from  the  top  did  not  re- 
duce the  temperature  perceptibly.  Removing  the  door  reduced 
it  a  few  degrees.  Removing  both  door  and  screw  caused  a  rapid 
decrease  from  320°  to  290°. 

"  2d  Series.  To  test  tJie  heat  of  oven  with  plaster  in  it.  I  filled 
a  half  flask  with  plaster  and  placed  it  in  the  oven,  with  a  ther- 
mometer on  the  floor  beside  it,  of  course  closing  the  door,  the 
outer  thermometer  standing  at  320°.     After  twenty  minutes  the 


598  MECHANICAL    DENTISTRY. 

inner  thermometer  had  reached  only  300°,  showing  the  cooling 
effects  of  the  plaster  on  the  air  of  the  oven.  Moved  the  ther- 
mometer on  to  the  plaster  ;  the  thermometer  fell  considerably, 
and  while  the  outer  thermometer  rose  in  thirty  minutes  to  440°, 
the  inner  reached  only  290°  ;  steam  was  then  admitted  to  the 
oven,  and  it  ran  instantly  up  to  340°  ;  steam  was  then  shut  off, 
and  the  outer  thermometer  maintained  at  about  360°  for  thirty 
minutes  longer,  by  which  time  the  inner  reached  320°.  At  this 
point  some  steam  was  let  off,  which  ran  the  outer  therm.ometer 
twenty  degrees  below  the  inner,  showing  that  plaster  is  slow  to 
part  with  its  heat  as  well  as  to  receive  it. 

"  Further  experiments  were  made  in  drying  plaster,  both  in  the 
oven,  with  steam  and  without  it,  and  out  of  the  oven  over  a  gas- 
burner  ;  also  with  plaster  mixed  with  pulverized  pumice  and 
mixed  with  marble  dust.  It  was  found  that  in  the  oven  with 
either  steam  or  dry  heat,  and  the  outer  thermometer  at  400°, 
about  thirty  minutes  were  required  to  dry  and  heat  a  small  half 
flask  of  plaster  to  320°,  and  about  two  hours  for  a  full  flask. 
Done  over  a  gas-burner,  under  an  inverted  flower-pot,  a  little  less 
time  was  consumed,  but  the  investments  loosened  from  the  flasks  ; 
under  higher  heats  they  become  burnt  and  badly  checked.  Those 
mixed  with  pumice  and  marble  dust  took  nearly  as  long  to  heat 
and  became  softer  than  the  plaster  alone,  and  so  were  thereafter 
abandoned. 

"  3d  Series.  Testing  cclhdoid  in  the  oven  ivitJiout  the  presence  of 
plaster,  steam,  or  pressure.  A  piece  of  celluloid  placed  in  the  oven 
at  320°,  the  heat  rising,  burned,  after  slight  swelling,  at  360°.  A 
second  piece  remained  in  thirty  minutes  with  the  heat  at  320°, 
swelled  slightly,  and  crumbled  to  powder  on  being  taken  out. 
A  third  piece  left  in  three  minutes  at  320°  was  taken  out  a  little 
swollen  and  somewhat  brittle  and  porous. 

"4th  Series.  Testing  celluloid  in  the  oven  zvitli  plaster  and  zvith 
moisture.  A  half  flask  of  moist  plaster  was  placed  in  the  oven, 
and  on  it  a  piece  of  celluloid  and  a  thermometer.  The  outer 
thermometer,  starting  from  320°,  rose  to  440°,  and  then  fell  to  360° 
in  about  sixty  minutes,  by  which  time  the  inner  thermometer 
reached  320°,  and  the  celluloid,  after  great  swelling,  ignited. 
(In  the  previous  series  of  experiments  the  celluloid  had  swollen 


CELLULOID    BASE. 


599 


but  about  one -tenth  as  much  as  it  did  in  these.)  Next  a  half 
flask  of  previously  dried  plaster  was  inserted,  and  the  inner  ther- 
mometer raised  to  340°,  when  a  piece  of  celluloid  was  dropped 
in,  and  burned  in  five  minutes.  A  second  piece  at  about  330° 
puffed  up  in  ten  minutes,  and  would  probably  have  exploded  in 
five  more  if  I  had  not  varied  the  experiment  by  admitting  steam 
to  test  its  effects,  which  were  a  greatly  increased  swelling  and 
then  gradual  shriveling  to  a  thin  wafer.  (That  steam  does  not 
produce  ignition  was  also  demonstrated  elsewhere,  when  its  ad- 
mission ran  the  inner  thermometer  up  to  340°,  and  yet  afterward, 
when  the  steam  was  shut  off,  the  celluloid  burned  at  320°.)  In 
the  next  test  the  dry  half  flask  was  again  used,  but  the  outer 
thermometer  was  lowered  to  320°,  which  ran  the  inner  one  down 
much  lower,  but  in  forty  minutes  they  tallied,  during  which  forty 
minutes  the  celluloid  after  the  first  fifteen  minutes  began  to  puff, 
and  in  ten  minutes  more  had  reached  full  size,  and  then  for  fifteen 
minutes  slowly  shrank,  then  exploded. 

"  Both  thermometers  being  now  at  320°,  a  piece  of  blank  was 
left  in  fifteen  minutes,  and  on  being  taken  out  crumbled  to 
powder  under  the  slightest  pressure.  A  second  blank,  in  twenty- 
five  minutes,  at  300°,  came  out  not  crumbling  so  badly.  A 
third  at  280°,  for  thirty  minutes,  was  slightly  swelled  and  some- 
what brittle  and  porous. 

"  5th  Series.  Testing  celluloid  in  the  oven  with  pressure  and 
plaster.  A  full  flask  of  plaster  was  placed  in  the  oven,  and  its 
temperature  raised  to  that  of  the  outer  thermometer,  320°  ;  then 
a  piece  of  celluloid  was  placed  in  the  flask,  which  was  closed 
down  in  three  minutes,  and  in  five  more  the  piece  was  removed 
from  the  flask  in  perfect  condition.  A  second  piece  was  then 
inserted,  closed  in  ten  minutes,  and  removed  from  the  oven,  and 
in  five  minutes  more  opened  in  perfect  condition.  A  third  piece 
was  left  in  twenty  minutes,  and  in  five  more  opened  in  perfect 
condition,  not  even  discolored.  A  fourth  piece  was  given 
twenty-five  minutes  in  the  oven  and  ten  more  before  opening 
the  flask  with  disastrous  results ;  it  had  crumbled  to  a  brown 
powder. 

"  This  fifth  series  of  tests  show  that  the  material  in  question 
remains  perfect  under  pressure  longer  than  without  it.     But  it 


600  MECHANICAL    DENTISTRY. 

is  to  be  remembered  that  the  investment  here  used  must  have 
lost  some  of  its  heat  while  out  of  the  oven.  Later  trials  seem 
to  indicate  tzventy  viimitcs  as  the  lo)igest  time  that  celluloid  can 
safely  be  left  at  320°.  As  a  side  issue,  the  cohesion  of  the 
material  was  tested  during  this  series ;  freshly-filed  surfaces 
were  placed  together,  and  apparently  joined,  but  they  separated 
under  a  strong  strain. 

"  6th  Series.  Testing  the  effect  of  steam  on  the  celluloid  at  320°. 
The  same  investment  was  used  as  in  Series  5,  and  the  flask 
closed  in  ten  minutes,  when  steam  was  admitted.  In  ten  minutes 
more  the  blank  came  out  spoiled,  being  disintegrated,  whitish 
and  sticky.  I  have  seen  celluloid  take  on  this  soft  and  white 
condition  when  heated  in  water  above  270°. 

"  7th  Series.  Testing  the  floiuing  qualities  of  celluloid  at  320°.  A 
piece  of  celluloid  was  placed  in  a  flask  heated  to  320°,  no  cavity 
being  left  in  the  plaster  to  receive  the  celluloid.  Closed  in  ten 
minutes.  It  sunk  a  bed  for  itself  in  the  hard  plaster,  flowing 
but  little.  This  is  a  hint  as  to  the  cause  of  misfits,  raised  bites, 
and  thickened  palates,  of  plates  molded  with  soft  plaster  and 
low  heats. 

8th  Series.  Testing  the  effects  of  quick  closing.  A  full  blank 
was  placed  in  a  full  flask  of  plaster  heated  to  320°,  and  closed 
so  that  the  halves  of  the  flask  came  together  on  one  side  con- 
siderably sooner  than  on  the  other.  Gave  it  over  fifteen  minutes 
in  the  oven.  When  opened  it  showed,  as  expected,  the  side  of 
the  plate  which  had  been  the  latest  closed  porous  and  brittle. 
As  a  side  issue  in  this  experiment,  tin  foil  of  two  thicknesses,  18 
and  60,  were  placed  side  by  side  on  the  blank,  and  when  peeled 
off  the  surface  below  was  of  a  browner  color  than  the  adjacent 
celluloid. 

"I  would  hint  at  the  possibility  of  the  celluloid  which  oozes 
from  the  flask,  and  touches  the  wall  of  the  oven,  being  ignited 
thereby  in  some  instances.  A  deep  excess-chamber  should  be 
cut  around  the  model  to  prevent  this.  Moreover,  this  escaped 
celluloid,  not  being  under  pressure,  is  doubtless  more  liable  to 
burn. 

"  Celluloid  hardens  on  being  subjected  to  dry  heat,  but  much 
of  this  is  not  desirable,  as  its  hardness  is  external,  while  inside 


CELLULOID    BASE.  6oi 

it  becomes  porous,  and  when  thus  hardened  is  very  brittle. 
Celluloid  will  burn  under  water,  as  demonstrated  in  a  vulcanizer, 
at  320°. 

"  Thin  edges  of  celluloid  will  soften  in  hot  drinks  in  the 
mouth.  Thus,  the  festoons  of  gum  left  thin  will  shrink  from 
the  tooth,  producing  what  may  be  termed  a  free  edge  of  celluloid 
gum,  under  which  dirt  deposits,  and  shows  through  the  semi- 
translucent  celluloid.  This  is  prevented  by  making  the  edges  of 
the  festoons  of  proper  thickness.  Another  error  frequently 
seen  is  that  of  cutting  away  the  interdental  celluloid  gum  (con- 
trary to  nature),  thus  forming  cavities  difficult  to  cleanse  by  the 
brush,  producing  unsightly  discoloration  at  those  points. 

"  The  principal  objection  to  celluloid  is  that  after  a  year  or  two- 
in  the  mouth  it  loses  its  beautiful  color,  and  becomes  of  a  dull 
vermilion  shade,  or  even  black.  This  will  probably  remain  the 
chief  objection  to  it.  That  it  is  not  so  tough  nor  so  elastic  as 
vulcanite,  and  that  in  consequence  it  wears  away  and  loses  its 
smooth  surface  in  the  mouth,  and  is  unfitted  for  clasps,  and  that 
it  is  a  little  more  difficult  to  work  than  rubber,  would  not  prevent 
its  popularity,  if  it- were  not  for  this  discoloration.  However, 
the  loss  of  color  does  not  always  extend  far  into  the  plate,  and 
much  of  it  may  be  quickly  removed  with  a  brush-wheel  and 
pumice." 

Finishing. — This  is  accomplished  with  the  use  of  the  same 
instruments  used  in  rubber  cases.  The  final  polish  may  be 
given  first  with  pumice-stone,  and  afterward  with  whiting  or 
Vienna  lime.  Dr.  H.  D.  Knight,  of  Lancaster,  Pa.,  recommends 
a  polish  obtained  by  rubbing  with  an  old  cloth  wet  with  cam- 
phor. This  may  be  valuable  between  teeth  and  in  places  inac- 
cessible to  the  brush- wheel.  In  finishing,  care  should  be  taken 
not  to  heat  the  plate  by  friction,  as  by  so  doing  the  surface  may 
be  injured  or  the  plate  sprung  out  of  shape. 

VULCANITE    BASE-PLATE    FACED    WITH    CELLULOID. 

The  above  method  of  constructing  an  artificial  denture,  de- 
signated by  the  inventor  as  the  "  New  Mode  Continuous-Gum  " 
process,  provides  for  the  use  of  single  porcelain  teeth  without 
artificial    gums,   the    latter  being    represented  by  the   celluloid 


602  MECHANICAL    DENTISTRY. 

facing.  This  expedient  is  most  esteemed  by  those  who  regard 
rubber  as  a  more  suitable  material  for  a  base  than  celluloid,  and 
who,  in  the  use  of  the  former,  are  unable  to  meet  the  require- 
ments of  a  certain  class  of  cases  with  either  single  gum  teeth  or 
sectional  blocks. 

In  this  combination  work,  which  admits  of  an  optional  ar- 
rangement of  each  individual  tooth,  the  conditions  are  secured 
which  better  enables  the  operator  to  effect  such  arrangement  of 
the  teeth  as  will  best  serve  the  purposes  of  mastication  and  aid 
in  restoring  the  customary  facial  contour  and  expression  of  the 
individual.  Still  other  advantages  are  claimed  for  this  method, 
namely,  that  the  rubber  is  stronger  and  more  elastic,  and,  being 
harder,  the  pins  are  less  liable  to  draw  or  loosen,  while  the  same 

Fig.  558. 


property  diminishes  the  liability  to  mechanical  abrasion  of  the 
palatal  surface  in  mastication,  and,  lastly,  that  in  case  of  acci- 
dent to  the  teeth  they  may  be  replaced  with  the  use  of  celluloid, 
thus  obviating  entirely  the  necessity  of  revulcanizing,  a  process 
which  always  impairs  the  structural  integrity  of  the  rubber. 

The  first  step  in  the  process  of  constructing  this  kind  of  work 
consists  in  molding  the  rubber  base-plate,  with  the  teeth  at- 
tached. All  the  preliminary  processes,  including  the  arrange- 
ment of  the  teeth,  are  the  same  as  those  practised  when  rubber 
alone  is  used.  The  teeth  employed  are  those  manufactured 
expressly  for  continuous-gum  work  and  celluloid,  as  shown  in 
F'ig-  55^-  I"  waxing  up  the  case,  all  the  exterior  surfaces  of  the 
teeth  and  marginal  portions  of  the  trial  plate  are  left  uncovered, 
and  a  strip  of  wax  arranged  all  along  the  external  border  of  the 


CELLULOID    BASE.  603 

wax  plate  to  form  a  groove  for  the  celluloid,  as  shown  in  Fig. 
558.  The  excavation  thus  formed  exteriorly  should  extend  in- 
wardly into  the  interdental  spaces  far  enough  to  secure  anchor- 
age for  the  celluloid  in  connection  with  that  obtained  by  the 
grooved  border.  The  space  or  spaces  for  the  celluloid  facing 
being  thus  provided  for,  the  palatal  portion  is  properly  con- 
toured, the  case  flasked,  packed,  and  vulcanized  in  the  usual 
manner.  The  piece,  when  removed  from  the  flask,  will  exhibit 
an  undercut  groove  along  the  border,  and  the  external  portions 
of  the  crowns  and  roots  exposed  in  the  manner  shown  in  the 
illustration. 

The  second  step  in  the  operation  consists  in  molding  the  cellu- 
loid facing.  The  following  is  the  method  of  forming  the  matrix 
and  molding  the  celluloid  :  Fill  up  all  the  space  between  the 
rimmed  border  of  the  plate  and  crowns  of  the  teeth  with  wax 
and  paraffin,  as  being  preferable  to  wax  alone,  and  then  contour 
it  exactly  as  required  in  the  finished  piece;  cover  with  tin  foil, 
and  stipple  the  surface  in  the  manner  heretofore  described.  The 
case  thus  prepared  is  ready  to  be  invested  for  the  purpose  of 
obtaining  the  matrix  in  which  to  mold  the  celluloid.  In  so  doing, 
fill  the  lower  section  of  the  flask  partly  with  plaster,  and  also  the 
palatal  portion  of  the  plate,  and  then  place  the  latter  in  the  flask 
with  the  teeth  upward,  raising  the  front  part  of  the  plate  somewhat, 
giving  it  a  downward  inclination  posteriorly,  in  order  that  the 
upper  section,  when  the  investment  is  completed,  may  be  de- 
tached without  dragging.  The  plate  should  not  be  imbedded 
in  the  plaster  beyond  the  grooved  margin,  making  the  line  of 
separation  on  the  outside  along  the  border  from  heel  to  heel  of 
the  plate.  Additional  plaster  is  now  poured  in,  covering  the  en- 
tire palatal  face  of  the  plate  and  crowns  of  the  teeth,  leaving 
only  the  outer  portions  of  the  latter  and  the  plate  exposed. 
When  the  plaster  sets  somewhat,  pour  in  more  plaster  around 
the  inner  edge  of  the  flask  ring,  forming  a  ridge,  and  also  a  cor- 
responding groove  or  space  between  it  and  the  plate.  The  piece 
thus  invested  will  present  the  appearance  shown  in  Fig.  559. 
The  surface  of  the  plaster  is  now  varnished,  and  thin  oil  applied 
to  all  the  surfaces.  When  the  wax  facing  is  covered  with  tin 
foil,  the  latter  should   not  be  oiled,  as  it  is  intended  that   this 


604 


MECHANICAL    DENTISTRY. 


shall  adhere  to  the  plaster  when  the  flask  is  separated.  The  in- 
vestment is  now  completed  by  adjustinf^  the  upper  section  of 
the  flask  and  filling  it  with  plaster.  When  sufficiently  hard, 
the  sections  are  carefully  separated  and  the  wax  thoroughly  re- 
moved with  boiling  water.  The  tin  foil  will  remain  adherent  to 
the  plaster  in  the  upper  section. 

Select  a  celluloid  blank  of  suitable  size  and  saw  ofiT  the  outer 
rim,  as  shown  in  Fig.  560.     Dress  and  carve  this  to  near  the  size 

Fir..   559. 


and  form  of  the  space  to  be  filled,  having  some  excess  of 
material.  Having  first  softened  the  rim  thus  prepared  by  im- 
mersing it  in  boiling  water  for  a  few  moments,  remove,  press  it 
well  into  the  space  provided  for  it,  and  hold  there  until  rigid. 
Place  the  two  sections  of  the  flask  together  in  their  proper  rela- 
tion, introduce  into  the  oven  previously  heated,  and  close  the 
flask  in  the  usual  way.  When  the  piece  is  removed  from  the 
flask,  and  the  tin  foil  removed  by  peeling  it  from  the  surface,  to 
which  it  will  adhere,  little  will  be  required  in  the  way  of  finish- 


CELLULOID    BASE. 


605 


ing  except  to  remove  surplus  material  at  the  necks  of  the  teeth 
and  borders  of  the  plate,  and  final  smoothing  andjpolishing  at 
these  points.  If  the  facing  material  has  been  stippled,  the  fin- 
ished piece  will  present  the  appearence  shown  in  Fig.  561. 

Fig.  560. 


The  above  process  is  also  applicable  to  gold  and  cast  metallic 
plates. 

ZYLONITE.  * 

"  A  modified  form  of    celluloid  has  been    introduced    under 
the  name  of  zylonite,  the  working  results  of  which  appear    to 

Fig.   i;6i. 


show  some  difference  in  quality.  Zylonite,  like  celluloid,  is 
composed  of  pyroxylin  and  camphor,  but  in  different  propor- 
tions, being,  it  is  claimed,  a  chemical  combination,  while  cellu- 
loid is  a  mechanical  mixture. 


*  Harris'  "  Principles  and  Practice  of  Dentistry." 


6o6  MECHANICAL    DENTISTRY. 

"  Possessing  translucency,  the  effect  of  zylonite  in  the  mouth 
is  very  pleasing,  and,  so  far  as  it  has  been  tested,  promises  to  be 
more  durable  than  celluloid,  without  the  tendency  to  warp  or 
to  change  color  when  ordinary  care  is  taken  in  its  manipulation, 
which  is  the  same  as  for  celluloid.  The  zylonite  blanks  are  uni- 
form in  color,  and  although  this  material  requires  the  same 
amount  of  pressure  to  mold,  it  flows  with  a  more  perfect  sharp- 
ness of  outline  than  celluloid,  and  apparently  does  not  disin- 
tegrate." 


CHAPTER  XV. 

ATTACHING  PORCELAIN  TEETH  TO  A  METALLIC  BASE 
WITH   RUBBER  OR  CELLULOID. 

The  following  method  of  attaching  porcelain  teeth  to  a  metallic 
plate  by  means  of  rubber  or  celluloid,  though  but  little  practised 
heretofore,  is  attracting  more  attention  than  formerly,  and  is 
eminently  deserving  of  more  favorable  consideration  and  general 
adoption,  by  reason  of  its  conspicuous  and  acknowledged  merits, 
than  it  has  ever  yet  received.  The  credit  of  its  first  introduction 
to  the  notice  of  the  profession  is  due  to  Dr.  P.  G.  C.  Hunt,  of 
Indianapolis,  Ind.,  who  practised  the  method  as  early  as  1859, 
and  whose  published  descriptions  of  the  manner  of  preparing  the 
plate  base,  substantially  the  same  as  that  for  which  Mr.  S.  D. 
Engle,  of  Hazleton,  Pa.,  obtained  letters-patent  some  years  later, 
.were  given  in  the  first  edition  of  this  work. 

In  commenting  on  this  method,  Professor  Charles  J.  Essig 
very  justly  remarks  that,  by  the  means  here  indicated,  we  are 
*'  able  to  produce  an  artificial  denture  embracing  all  that  is  good 
in  metallic  and  vulcanite  work,  at  the  same  time  avoiding  the 
great  defects  of  each." 

That  it  possesses  marked  advantages  over  the  method  of 
attaching  teeth  to  a  metallic  plate  base  by  soldering  is  unques- 
tionable. The  waste  and  consequent  change  in  the  form  of  the 
plate  incident  to  soldering,  so  inseparable  from  the  older  method 
of  attachment  by  means  of  stays  or  backings,  is  wholly  avoided  ; 
the  strain  upon  the  platina  pins  is  greatly  lessened  by  reason  of 
the  perfectly  adapted  rubber  or  celluloid  socket  in  which  each 
tooth  or  block  securely  rests;  the  liability  to  fracture  of  the 
teeth  from  concussion  or  violence  is  materially  diminished  on 
account  of  the  pliable  nature  of  the  attaching  material  used  ; 
a  near  approximation  to  the  natural  form  of  the  ridge  or  gum  on 
the  lingual  side  of  the  plate  is  secured  ;  the  rubber  or  celluloid, 
penetrating  all  the  joints  and  openings  between  and  beneath  the 

607 


6o8  MECHANICAL    DENTISTRY. 

teeth,  renders  the  piece  wholly  impervious  to  the  oral  secretions, 
making  it,  in  point  of  cleanliness  and  purity,  equal  to  continuous- 
gum  work;  the  facility  with  which  injury  to  the  teeth  may  be 
repaired;  the  practicability  of  remodeling  the  piece  without  im- 
pairment of  the  teeth  or  plate;  its  susceptibility  of  receiving  a 
final  finish  excelled  by  no  other  method  in  point  of  artistic 
beauty  ; — these  are  among  the  qualities  which  commend  this 
method  of  substitution  as  one  of  peculiar  merit  and  excellence. 

In  mounting  teeth  by  this  method,  preference  should  be  given 
to  either  gold,  platinum,  aluminum,  or  cast  metal  as  a  base.  When 
silver  is  used,  the  plate  should  be  made  from  refined  silver  al- 
loyed with  platinum,  with  the  additional  precaution  of  interposing 
a  layer  of  tin  foil  between  the  rubber  and  plate,  an  expedient  not 
necessary  when  celluloid  is  employed.  Aluminum  has  a  limited 
adaptability  to  this  mode  of  substitution,  but  requires  special 
treatment  in  its  preparation  for  the  purpose,  a  description  of 
which  will  be  given  in  connection  with  the  manner  of  preparing 
the  plate. 

The  manipulative  details  concerned  in  the  construction  of  an 
artificial  denture  by  the  method  under  consideration  are  thus 
described  by  Dr.  Hunt: — 

"  Take  the  impression,  make  metallic  dies,  and  form  the  plate 
as  for  work  in  the  ordinary  way.  After  fitting  the  plate  in  the 
mouth,  get  the  articulation,  the  fullness  and  length  of  the  teeth, 
remove  the  wax  and  plate  from  the  mouth,  and  make  the  plaster 
articulation.  If  a  full  set,  after  separating  the  articulation,  and 
before  removing  the  wax  from  the  plate,  take  a  small,  light  pair 
of  dividers,  set  them  say  one  inch  apart,  and  with  one  point  fol- 
lowing the  margin  of  the  wax,  representing  the  cutting  edge  of 
the  teeth,  and  the  other  point  marking  permanently  the  plaster, 
you  have  always  in  the  dividers  so  set  a  gauge  for  the  length  of 
any  particular  tooth.  A  convenient  substitute  for  the  dividers 
may  be  formed  from  a  piece  of  wire  of  convenient  length,  one- 
half  the  diameter  of  a  common  excavator,  by  suitably  twisting 
its  middle  for  a  handle,  and  its  ends  being  sharpened,  and  point- 
ing in  the  same  direction,  one  or  one  and  a  half  inches  apart. 

"  Thus  far  we  proceed  as  we  do  for  ordinary  gold  work.  We 
will  now  suppose  the  teeth  ground  and  jointed,  leaving  as  much 


METALLIC    BASE    WITH    RUBBER    ATTACHMENT, 


609 


space  between  the  teeth  and  plate  as  the  plate  will  admit  of.  We 
next  mark  with  a  sharp-pointed  instrument  on  the  labial  surface 
of  the  plate  each  point  where  it  is  necessary  to  place  a  loop  for 
purposes  hereinafter  described.  Then  apply  wax  to  the  external 
or  labial  parts  of  the  teeth  and  plate  in  any  manner  sufficient  to 
retain  the  teeth  in  position,  remove  the  wax  from  the  lingual 
parts  of  the  teeth  and  plate,  and  mark  the  position  on  the  metal 
where  it  is  desirable  to  insert  loops,  remove  the  teeth  and  wax, 
and  with  a  small  bow-drill  make  holes  through  the  plate  at  the 
several  points  previously  determined  on  for  the  attachments, 
about  the  size  of  the  ordinary  plate  punch-hole,  take  a  wire,  or 
ordinary  gold  plate,  cut  in  strips,  say  from  a  half  to  one  line  in 

Fig.  562. 


width,  being  governed  b\'  the  amount  of  room  there  is  under  the 
base  of  the  teeth,  and  with  small,  round-nosed  pliers,  bend  the 
strip  around,  grasp  both  ends  with  square-nosed  pliers,  draw  the 
round-nosed  pliers  from  the  loop,  still  grasping  the  square-nosed 
pliers  with  the  left  hand,  and  with  a  hammer  strike  the  top  of 
the  loop  a  sufficient  blow  to  keep  the  ends  from  springing  apart. 
Cut  off  the  ends,  and  dress  down  to  fit  the  holes  in  the  plate, 
after  w^hich  solder  on  charcoal  or  other  suitable  substance  with- 
out investment." 

By  reference  to  Fig.  562,  which  illustrates  Mr.  Engle's  method 
of  providing  attachment  for  the  rubber  to  the  plate  by  means  of 
bent  or  hooked  wires  soldered  to  the  base,  the  substantial  iden- 
39 


6lO  MECHANICAL    DENTISTRY. 

tity  of  Dr.  Hunt's  mode  of  forming  loops  for  the  same  purpose 
will  be  apparent. 

With  this  digression,  we  return  to  Dr.  Hunt's  instructions: — 

"  Pickle,  dress,  and  polish  that  portion  of  the  plate  to  be 
exposed  to  view.  Bend  and  flatten  the  pins,  arrange  the  teeth 
according  to  the  articulation,  waxing  so  as  to  cover  up  the  loops 
if  practicable  ;  the  loops  should  be  placed  as  near  the  base  of  the 
teeth  as  possible,  the  rubber  forming  when  finished  a  part  of  that 
general  concave  shape  which  is  desirable  in  upper  dentures,  and 
which  is  not  possible  to  obtain  with  the  ordinary  soldered  work. 
Then  with  silicate  of  soda  paint  the  joints,  to  keep  the  rubber 
from  forcing  in  where  it  would  show  after  vulcanizing.  Flask, 
vulcanize,  and  finish  up  as  usual.  The  advantages  of  this  style 
of  work  are  obvious.  With  this  you  have  work  as  cleanly  as  the 
continuous  gum,  decidedly  more  so  than  the  very  best  single 
gum  or  block-work  soldered  in  the  usual  way  ;  again,  it  is  very 
much  stronger,  less  liable  to  breakage,  both  in  and  out  of  the 
mouth,  as  the  rubber  gives  a  perfect  base  and  support  for  the 
teeth  to  set  upon.  By  this  method  tliere  is  no  springing  of  plates. 
As  your  plate  fits  the  mouth  when  the  articulation  was  taken,  so 
will  be  the  fit  when  the  case  is  completed. 

"  On  the  labial  edge  of  the  upper  plate,  the  rubber  may  be 
allowed  to  project  beyond  the  edge,  if  desirable,  and  it  will  be 
found  in  many  cases  exceedingly  satisfactory  to  do  so,  and  allow 
the  rubber  to  be  of  considerable  thickness  near  the  alas  of  the  nose, 
where  the  loss  of  the  cuspidati  may  leave  a  want  of  support  to 
the  soft  parts  adjacent,  and  which  in  this  manner  can  be  readily 
corrected.  If  the  rubber  extends  upward  so  far  as  to  irritate  the 
muscular  structure,  a  few  minutes  will  be  sufficient  to  make  the 
necessary  alterations.  In  all  such  cases  where  we  have  control 
of  our  patients,  we  place  the  denture  in  the  mouth  before  finally 
polishing,  so  as  to  determine  as  accurately  as  possible  the  limit 
to  which  extension  upward  may  be  carried. 

"  The  neatest  work  on  this  principle  is  made  by  carving  blocks, 
giving  to  the  lingual  surface  that  regular  concave  form  which  is 
desirable.  In  this  no  platinum  pins  or  loops  are  necessary,  but 
in  that  half  of  the  matrix  on  which  the  blocks  are  carved,  large 
metallic  pins  are  so  arranged  as  to  be  hid  from  view  in  the  tooth 


METALLIC    BASE    WITH    RUBBER    ATTACHMENT.  6l  I 

body.  Different-sized  pins  may  be  used,  as  large  as  the  nature 
of  the  case  will  admit.  In  short,  we  make  the  holes  in  the  block 
similar  to  those  in  pivot  teeth,  where  there  is  not  sufficient  room 
in  the  block  above  the  tooth  (or  below  if  an  under)  to  allow  the 
pins  to  run  into  the  body  of  the  teeth.  After  burning,  grinding, 
and  fitting,  get  the  position  of  the  holes  in  the  blocks  relative 
to  the  plate,  and  drillthrough  the  plate  as  before,  and  instead  of 
loops,  solder  gold  wire  of  suitable  size  and  length,  say  a  very 
little  shorter  than  the  depth  of  the  hole  in  the  blocks,  and  two- 
thirds  the  diameter  thereof ;  the  wire  should  have  a  screw-thread 
cut  on  it,  or  that  which  is  just  as  good  and  more  expeditious, 
barb  or  cut  with  a  sharp  knife.  At  this  point  of  the  manipula- 
tion, if  it  is  desired  that  the  rubber  should  extend  beyond  the 
labial  or  buccal  edge  of  the  metallic  plate,  place  as  many  loops 
at  different  points  as  are  sufficient  to  retain  it  with  firmness, 
after  which  polish  the  plate,  wax,  and  proceed  as  before  described. 
If  you  desire  no  rubber  beyond  the  blocks,  the  roughness  of  the 
holes  in  the  same,  and  the  barbed  points  on  the  gold  wire  when 
properly  packed  and  vulcanized,  will  give  ample  strength  and 
firmness  to  the  case,  and  if  care  has  been  used  in  the  entire  man- 
ipulation, you  will  have,  when  finished,  but  a  thin  line  of  rubber 
exposed  to  view. 

"  In  partial  cases,  if  of  gold  base,  solder  on  loops,  as  before,  for 
the  retention  of  the  teeth,  and  if  there  are  to  be  any  clasps,  make 
them  of  rubber,  uniting  them,  as  the  teeth,  with  loops.  *If  the 
ordinary  plate  teeth  are  used,  it  is  frequently  necessary  to  back 
them  to  give  better  retaining-points  for  the  rubber.  If  blocks 
are  to  be  burned,  insert  loops  of  platinum  plate  in  the  shape  of 
the  letter  U  in  place  of  the  platinum  wire  pins.  In  consequence 
of  the  affinity  of  the  sulphur  in  the  vulcanite  for  silver,  plates 
of  that  metal  should  not  be  used." 

Dr.  A.  S.  Richmond,  in  the  Dental  Cosmos,  recommends  the 
following  method  of  securing  attachment  of  the  vegetable  plastics 
to  the  base-plate  : — 

"The  method  consists  in  punching  the  plate  with  holes  with  a 
punch  devised  for  the  purpose  and  herewith  illustrated  (Fig.  563), 
forming  a  number  of  depressions  or  pits  in  the  palatal  surface, 
which  might  be  termed  small  air-chambers,  and  they  certainly 


6l2 


MECHANICAL    DENTISTRY. 


assist  materially  as  such,  especially  in  lower  dentures,  where 
the  holes  are  punched  in  a  row  on  the  outside  and  inside  about 
one-fourth  of  an  inch  apart  and  one-eighth  of  an  inch  from  the 
margin  (Fig.  564).  For  upper  dentures,  where  the  undercut  or 
recession  of  the  maxillary  ridge  is  so  abrupt  as  to  make  it  im- 
possible to  swage  a  plate  to  a  proper  fit,  the  plate  can  be  trimmed 
to  suit,  making  the  upperportion  of  rubber,  the  perforation  form- 
ing a  firm  attachment.  I  also  send  a  three-quarter  plate  to  show 
the  method.  There  is  no  danger  of  springing  the  plate  if  proper 
care  is  used,  and  if  by  accident  it  should  be  out  of  shape,  it  is 
an  easy  matter  to  set  it  right  by  burnishing  it  upon  the  die. 


Fig.  563. 


Fig.  564. 


"  I  have  used  this  method  exclusively  for  a  number  of  years, 
and  have  never  had  any  objection  offered  by  patients  on  account 
of  the  perforations. 

"  Dr.  John  H.  Meyer,  of  this  city,  showed  me  some  time  ago 
a  continuous-gum  denture  in  which  the  entire  surface  of  the 
plate  was  perforated  with  small  holes,  thereby  reducing  the  weight 
of  the  metal  about  one-half,  and  making  the  most  perfect  attach- 
ment of  the  body,  the  perforations  also  assisting  as  small  air- 
chambers." 

The  following  unique  and  original  method  of  casting  a  metal 
base-plate,  fastenings  and  hooks,  in  a  single  piece,  is  thus 
described  by  Dr.  Norman  W.  Kingsley  :  "  The  plate  is  formed  of 


METALLIC    BASE    WITH    RUBBER    ATTACHMENT,  613 

a  thin  sheet  of  wax  set  up  on  the  plaster  model,  but  before  it  is 
flasked  for  casting  I  take  a  dozen  small  gimp  tacks,  with  half 
round  heads,  and  set  them  in  a  row  upon  the  ridge  of  the  lower 
jaw,  with  their  heads  just  imbedded  in  the  wax,  and  then  flask 
the  piece.  In  flasking  it,  I  use  plaster  and  sand,  in  the  propor- 
tions of  about  three  parts  of  sand  to  one  of  plaster.  This  gives 
a  fine  surface  when  it  comes  in  contact  with  the  wax  in  making 
the  mold,  and  it  is  sufficiently  porous  to  dry  out  quickly.  When 
the  flask  is  opened,  the  wax  is  readily  removed  ;  the  tacks  are 
pulled  out,  and  when  the  casting  is  made  the  spaces  that  were 
occupied  by  the  tacks  are  filled  with  the  metal,  so  that  we  have 
a  plate  with  a  row  of  tacks  of  the  same  metal,  which  can  be 
easily  bent  for  attachments,  standing  around  upon  it." 

If  gum  sections  are  used  in  connection  with  a  plate  formed 
in  the  manner  just  described,  vulcanite  may  be  employed  as  a 
means  of  attachment,  but  plain,  single  teeth  are  equally  admissi- 
ble in  the  use  of  either  rubber  or  celluloid.  The  particular  alloy 
used  by  Dr.  Kingsley  in  casting  plates,  and  of  which  he  speaks 
in  terms  of  high  commendation,  consists  of  pure  tin  and  bismuth, 
in  the  proportion  of  one  pound  of  the  former  to  one  ounce  of 
the  latter. 

The  following  method  of  preparing  aluminum  plates  for  the 
attachment  of  the  rubber  was  communicated  to  the  author  by 
Dr.  J.  W.  Hollingsworth,  of  Greencastle,  Indiana,  an  intelligent 
practitioner  Vv-ho  has  had  long  and  extended  practical  experi- 
ence in  the  various  modes  of  working  this  metal  for  dental  pur- 
poses, and  v/ho  says  of  the  following  mode  of  procedure  that 
"  it  is  the  most  practicable  and  the  most  easily  manipulated 
method  that  I  have  yet  seen." 

The  following  is  tlie  manner  of  preparing  the  plate  as  de- 
scribed by  Dr.  Hollingsworth  :  "  Perforate  the  ridge  of  the 
plate  at  proper  points  and  intervals  ;  then  pass  through  these 
perforations,  from  the  inner  surface  of  the  plate,  headed  pins 
made  of  aluminum,  which,  after  replacing  the  plate  with  the 
pins  back  upon  the  die,  we  shrink  down  to  permanency  with  a 
hollow  punch.  The  punch  must  be  made  with  the  hole  not  quite 
equal  in  depth  to  the  length  of  the  e.xtruding  portion  of  the  pins 
and  slightly   bell-mouthed.     The  riveting  process  forms   seriate 


6l4  MECHANICAL    DENTISTRY. 

studs  or  pins,  which  may  be  bent  or  flattened  with  pHers  in  any 
way  to  suit  the  requirements  of  the  case." 

When  celluloid  is  used  for  purposes  of  attachment  in  the  case 
of  full  upper  dentures,  the  palatal  portion  of  the  blank  should 
be  cut  or  sawed  away,  leaving  only  the  ridge  portion  to  be  used, 
and  this  should  be  trimmed,  if  necessary,  so  as  to  have  but  little 
excess  of  material.  The  ordinary  full  blank  may  be  used  for 
lower  cases,  observing  the  same  precautions  in  regard  to  quantity 
of  material.  When  the  blank  is  thus  prepared,  the  subsequent 
manipulations  are  the  same  as  those  described  in  connection 
with  the  celluloid  base. 

It  may  be  observed  that,  when  rubber  or  celluloid  is  used,  it 
is  better  to  dispense  with  the  plaster  model  in  forming  the  mold 
or  matrix,  and  proceed  as  follows  :  When  the  teeth  are  arranged, 
and  the  required  contour  and  fullness  given  to  the  wax  drafts, 
fill  the  lower  section  of  the  flask  with  plaster,  and  (having  also 
filled  the  plate  with  the  same)  embed  the  plate  in  it,  making  the 
dividing  line  on  the  external  rim  of  wax.  When  the  plaster  has 
hardened,  and  the  other  section  formed,  and  the  two  afterward 
separated,  the  metallic  plate  will  remain  in  the  lower  section 
and  the  teeth  in  the  upper. 

When  using  celluloid,  plain  teeth  may  be  advantageously 
employed,  the  former  representing  the  gum  ;  this  gives  perfect 
freedom  in  the  arrangement  of  each  separate  tooth  in  the 
denture,  an  optional  disposition  the  importance  of  which  cannot 
be  over-estimated. 


CHAPTER  XVI. 
CAST  METAL  BASE. 

Cheoplastic  Process. — The  method  of  mounting  artificial 
dentures  by  what  is  familiarly  known  as  the  "cheoplastic  pro- 
cess," in  which  the  base  consists  of  certain  metallic  com- 
pounds or  alloys  in  cast  form,  has  comparatively  but  limited 
application  in  prosthetic  practice.  The  method,  as  commonly 
practised,  is  rarely  applied  to  full  upper  cases,  occasionally 
to  partial  upper  pieces,  but  chiefly  to  lower  dentures  in  cases  of 
unusual  absorption  of  the  alveolar  ridge,  requiring  increased 
weight  to  secure  adequate  stability  of  the  substitute.  The  alloys 
in  most  general  use  for  this  purpose  are  those  compounded  by 
Drs.  Wood,  Weston,  and  Watt,  whose  names  are  a  sufficient 
guarantee  of  the  suitableness  of  those  several  alloys  for  the  pur- 
pose. 

The  construction  of  a  denture  by  this  method  is  readily  ac- 
complished by  any  one  familiar  with  the  working  of  vulcanite 
or  celluloid.  The  manipulations  concerned  in  the  formation  of 
a  mold  or  matrix  are,  in  general,  the  same  as  those  employed 
in  forming  a  matrix  for  rubber  or  celluloid.  The  model  and  in- 
vesting material,  however,  must  be  of  such  substances  as  main- 
tain their  integrity  of  form  perfectly  under  the  heat  necessarily 
applied  in  thorough  drying  of  the  case  and  contact  of  molten 
metals.  Simple  plaster,  on  this  account,  is  unsuitable,  either  for 
the  model  or  investment,  and  it  is  customary,  therefore,  to  add 
to  it,  in  relatively  large  proportions,  such  substances  as  undergo 
but  little,  if  any,  change  of  form  when  exposed  to  the  necessary 
heat.  Those  most  commonly  employed  are  finely  pulverized 
pumice-stone,  marble-dust,  soapstone  powder,  or  clean  white 
sand.  In  the  use  of  either  of  these  substances,  only  enough- 
plaster  should  be  added  to  give  to  the  molding  material  sufficient 
body  or  strength  necessary  to    provide  against  defacement    in 

615 


6i6 


MECHANICAL    DENTISTRY. 


handling,  say  one   part  plaster  to   three   of  sand,  which  is  the 
mixture  generally  employed. 

One  of  the  best  adapted  flasks  for  molding  and  casting  pur- 
poses, contrived  by  Prof.  George  Watt,  is  exhibited  in  Fig.  565. 
The  piece,  properly  prepared  by  careful  contouring  of  the  wax 
or  paraffin,  is  then  flasked  in  the  same  manner  as  when  pre- 
paring a  mold  for  vulcanite.  When  the  sections  of  the  flask 
are  separated,  grooves  or  gateways  should  be  cut,  extending 
from  the  posterior  and  lateral  margins  of  the  mold  to  the  open- 
ings on  either  side,  shown  in  the  figure,  thus  providing  for  the 

Fin.  565. 


ingress  and  egress  of  the  melted  metal  when  poured;  after  which 
all  traces  of  wax  should  be  thoroughly  washed  out  with  boiling 
water. 

The  sections  of  the  flask  are  now  adjusted  to  each  other,  and 
tightly  clamped,  to  prevent  the  escape  of  metal  when  poured. 
Before  casting,  the  mold  should  be  thoroughly  dried  by  expos- 
ing it  for  two  or  three  hours  to  an  oven  heat,  and  the  temper- 
ature, at  the  moment  of  pouring,  should  be  raised  to  about  that 
required  to  fuse  the  alloys  mentioned,  or  about  400°  to  440°  F. 

In  pouring  the  metal  into  the  mold  through  one  of  the  lateral 


CAST    METAL    BASE, 


617 


openings,  the  metal  should  rise  freely  and  quickly  into  the  oppo- 
site one,  and  if  bubbling  occurs,  which  will  never  happen  if  the 
piaster  has  been  sufficiently  dried,  the  flask  should  be  lightly 
tapped  on  some  hard  surface  until  the  ebullition  ceases,  thus 
insuring  a  more  certain  intrusion  of  the  metal  into  all  parts  of 
the  mold  before  solidification  takes  place. 

Fig.  566. 


Dr.  Weston  has  devised  a  casting  flask  (Fig.  566),  the  two  sec- 
tions of  which  form  an  encircling  band  with  the  sides,  or  top  and 
bottom,  open,  and  which  are  closed  securely  with  screw-bolts. 
This  form  facilitates  the  escape  of  moisture  from  the  plaster 
investment  in  the  process  of  drying. 


6l8  MECHANICAL    DENTISTRY. 

When  the  piece  is  quite  cold,  it  may  be  readily  removed  from 
the  flask  by  soaking  the  investing  material  for  a  few  minutes  in 
water. 

All  superfluous  metal  is  removed  with  suitable  instruments, 
and  all  surfaces  except  the  palatal  face  smoothed  and  polished, 
first  with  Scotch  stone  or  fine  emery  cloth,  and  finally  with  chalk 
used  upon  a  brush-wheel. 

If  there  are  any  narrow  spaces  or  interstices,  not  affecting  the 
integrity  of  the  plate,  that  are  not  completely  filled  at  the  time 
of  casting,  such  imperfections,  Dr.  Kingsley  suggests,  may  be 
readily  and  perfectly  repaired  with  amalgam. 

There  are  other  practicable  methods  by  which  cast  metallic 
plates  may  be  utilized  to  advantage,  and  their  application  to  the 
needs  of  the  practitioner  greatly  extended.  There  are  many 
cases  of  absorption  in  which  a  lower  denture  constructed 
entirely  of  cast  metal  would  be  objectionable  on  account  of 
excessive  weight.  In  such  cases,  a  plate  of  sufficient  thickness 
to  secure  tho  required  stability  may  be  cast,  and  the  teeth  sub- 
sequently attached  with  rubber  or  celluloid,  as  described  in 
connection  with  swaged  plates  ;  or  the  base-plate  may  be  cast 
in  the  form  of  the  rubber  base  described  in  connection  with  the 
New  Mode  Continuous-gum,  and  faced  in  the  same  manner  with 
celluloid, — either  method,  while  securing  the  requisite  weight, 
admitting  also  of  the  use  of  single  plain  teeth. 

GOLD    ALLOY    CAST    BASE. 

The  compound  of  gold,  silver,  and  tin,  in  varied  proportions, 
in  connection  with  specific  and  original  methods  of  casting 
dental  plates,  devised  and  patented  by  Dr.  George  F..  Reese,  of 
Brooklyn,  N.  Y.,  has  attracted  attention  as  a  possible  substitute 
for  the  plastic  vegetable  substances  so  commonly  employed  as  a 
base  for  artificial  dentures. 

After  premising  that  the  methods  in  common  use  for  casting 
alloys  were  not  applicable  to  one  having  the  molecular  proper- 
ties of  Reese's  compound,  the  inventor  says  he  was  led,  after 
multiplied  experiments,  to  adopt  the  plan  of  which  the  following 
is  a  description  : — 

The  impression  is  taken  with  plaster,  to  which  salt  or  sulphate 


CAST    METAL    BASE. 


619 


of  potassa  has  been  added,  and  the  model  obtained  from  this  with 
pure  plaster.  Upon  this  the  teeth  are  arranged.  For  the 
trial  plate,  gutta  percha,  paraffin,  and  wax,  or  modeling  com- 
pound, may  be  used.  When  satisfaction  in  the  occlusion  is 
obtained,  then  the  case  is  returned  to  the  model,  and  the  waxing 
around  the  labial  and  buccal  borders  of  the  teeth  completed. 
That  portion  of  the  trial  plate  which  covers  the  palatine  surface 
is  now  removed,  so  that  the  pins  of  the  teeth  will  be  nearly  ex- 
posed, allowing  the  wax  which  is  under  the  gum  to  remain. 
That  the  plate,  after  casting,  shall  not  be  too  cumbrous,  the  trial 

Fig.  567. 


plate,  which  has  been  removed,  must  be  substituted  with  two 
thicknesses  of  French  flower  wax,  cut  carefully  to  the  model, 
and  pressed  down  closely  with  the  finger  in  a  manner  that  no 
wrinkles  will  appear  to  mar  the  beauty  of  the  work. 

Fig.  567  represents  a  case  thus  prepared.  The  dotted  lines 
show  the  borders  of  the  thin  wax.  B,  A,  and  C,  represent 
nipples  of  solid  wax,  fixed  to  the  posterior  border  and  to  the 
tuberosities,  A  and  C  being  the  places  of  exit  for  the  molten 
metal  into  the  waste  pockets,  and  B  the  place  of  entrance  of 
the  metal  from  the  pouring-gaine. 


620 


MECHANICAL    DENTISTRY. 


The  case  is  now  transferred  to  the  small  brass  flask,  r, 
Fig.  568,  the  sections  of  which  have  been  well  oiled  upon 
the  inner  surface,  to  facilitate  their  removal  from  the  invest- 
ment. Either  section  is  then  placed  upon  a  plate  of  glass  and 
plaster  poured  into  it  until  half  filled.  The  model,  as  prepared, 
after  being  well  saturated  with  water,  is  embedded  in  this  single 
section,  allowing  the  teeth  and  gums  to  remain  uncovered.  Set 
on  the  counterpart  of  the  flask  and  add  more  plaster  along  the 


Fig.  56S. 


■n 

Case  Ready  for  the  Completion  of  Investment. 


posterior  border  until  the  nipples  are  reached  or  slightly 
covered.  After  this  has  set,  the  upper  section  may  be  removed 
and  the  surface  of  the  plaster  covered  with  a  thin  varnish  or 
soapy  water.  Return  the  section  and  complete  the  investment. 
Fig.  568  shows  the  case  thus  made  ready. 

After  a  proper  time  place  the  flask  in  hot  water,  that  it  may 
be  separated  without  injury.  When  separated,  wash  away  all 
the  wax,   and,  by   means   of  gentle   tapping,   remove  the   flask 


CAST    METAL    BASE. 


621 


rings  from  the  investment  and  set  them  aside.  The  depressions 
formed  by  the  nipples  may  now  be  extended  through  the  plaster 
to  the  external  edge  ;  or,  if  the  circumstances  of  the  case  make 
this  impossible,  the  channels  maybe  made  at  the  line  of  division 

Fig.  569. 


between  the  two  sections,  as  shown  by  the  dotted  lines  in  Figs. 
569  and  570.  Externally,  the  channels,  D,  E,  F,  Fig.  570, 
should  be  neatly  countersunk  and  varnished  with  shellac  to  re- 
ceive the  pockets.  The  latter  are  made  of  the  French  wax  by 
warming  and  wrapping  the  same  around  a  cone-shaped  stick 


622 


MECHANICAL    DENTISTRY. 


and  the  base  and  apex  of  the  cone  neatly  trimmed  of  all  ine- 
qualities. These  pockets  should  be  about  one  and  a  half  inches 
long,  and  about  half  an  inch  in  diameter  at  the  base,  and  an  eighth 
of  an  inch  at  the  apex.  The  pouring-gaine  is  made  in  the  same 
manner,  but  should  be  smaller  in  diameter  at  the  base  and 
about  two  inches  long.  After  removing  these  wax  covers  from 
the  molding  sticks,  the  larger  ends  of  each  should  receive  a  thin 
wax  cover  secured  to  its  place,  and  made  water-tight  by  flowing 
hot  wax  along  the  line  of  junction,  after  the  manner   of  solder- 

FiG.  570. 


Upper  or  Counter  Section  corresponding  to  Fig.  569.     D,  E,  F,  channels 
for  entrance  and  exit  of  metal. 


ing.  Trim  the  covers,  then  place  the  smallest  ends  of  the  large 
cones  in  the  countersunk  channels  at  the  tuberosities  and  the 
small  cone  in  the  middle  hole,  and  secure  them  with  melted 
wax.     Fig.   569,  d\  c' ,f' ,  shows  the  pockets  thus  attached. 

Should  the  channels  have  been  made  through  the  solid  plaster 
of  the  lower  section,  as  in  Fig.  569,  then  the  upper  section. 
Fig.  570,  need  not  be  joined  to  it  until  after  the  pockets  are 
secured   to  their  places.     Should,  however,  the   channels  have 


CAST    METAL    BASE. 


623 


been  made  upon    the   line   of  division,  then   the   sections   must 
be  joined  before  the  pockets  can  be  attached. 

The  case  is  now  ready  for  a  second  investment,  which  is  done 
in  a  flask  sufficiently  large  to  embrace  the  case  as  it  now  pre- 
sents. Fig.  571  represents  the  construction  of  the  large  flask. 
One  section  of  the  same  is  placed  upon  glass  and  about  half  filled 
with  plaster.  The  case,  having  been  well  soaked  with  cold 
water,  is  laid  carefully  upon  the  plaster,  allowing  the  long  cone 

Fig.  571. 


to  rest  in  the  notch  at  the  heel  of  the  flask,  and  the  waste  pock- 
ets to  become  embedded  in  the  plaster.  Immediately  put  the 
other  section  of  the  flask  in  place  and  complete  the  investment 
by  filling  with  plaster  the  uppermost  section  to  fullness.  Of 
course,  there  will  be  no  division  of  the  sections,  as  was  the  case 
in  the  former  flasking.  After  solidification,  the  pouring-gaine 
must  be  neatly  trimmed  and  countersunk,  and  great  care  must 
be  exercised  that  no  dirt  be  allowed  to  enter  the  channel. 

The  wax,  which  is  embedded  in  the  plaster,  and  which  forms 


624  MECHANICAL    DENTISTRY. 

the  waste  pockets,  will  be  entirely  absorbed,  and  no  trace  of  it 
will  be  seen  upon  opening  the  flask. 

All  is  now  ready  for  drying.  This  is  done  in  an  oven  spe- 
cially prepared  for  the  purpose,  but  it  may  be  accomplished  in 
any  way  to  be  chosen  by  the  manipulator.  An  ice-cold  mouth 
mirror  placed  over  the  opening  of  the  pouring-gaine  will  detect 
the  slightest  moisture  which  may  remain,  and  until  this  is  en- 
tirely dispelled   the  casting  should  not  be  attempted. 

There  are  several  grades  of  the  gold  alloy,  as  compounded  by 
Dr.  Reese,  to  melt  which  requires  a  heat  registering  from  600° 
to  700°  F.,  but  a  higher  temperature  than  this  must  be  attained 
before  pouring,  in  order  to  secure  a  satisfactory  flow.  At  900° 
rapid  oxidation  takes  place.  This,  of  course,  should  be  avoided. 
The  alloy  may  be  melted  in  an  ordinary  iron  ladle  or  crucible, 
over  a  gas  or  other  flame,  and  should  be  poured  while  the  mold 
is  hot. 

After  the  lapse  of  an  hour  or  two,  or  until  the  cast  is  suf- 
ficiently cooled  to  insure  the  integrity  of  the  teeth,  it  may  be 
placed  in  warm  water,  when  the  investment  can  be  easily  re- 
moved. 

Fig.  572  represents  the  cast  after  removal.  The  surplus  metal 
may  be  separated,  along  the  dotted  line  S,  with  a  ribbon  saw, 
after  which  the  denture  is  ready  for  the  pumice  wheel  and  brush. 
Fig.  573  represents  the  finished  case. 

Repairing. — The  process  of  repairing  broken  plates  is,  in 
principle,  the  same  as  above.  A  flask,  specially  constructed  by 
the  inventor,  is  used  for  this  purpose,  whereby  a  single  invest- 
ment suffices.  Suppose,  for  example,  a  plate  is  broken,  from  the 
labial  to  the  posterior  border,  along  the  median  line  ;  the  broken 
edges  are  scraped  clean,  and  a  separation  made  of  about  an 
eighth  of  an  inch.  The  parts  are  then  adjusted  upon  the  model, 
and  the  space  between  the  approximate  edges  filled  with  wax. 
At  each  extremity  of  the  fissure  a  pencil  of  wax,  an  eighth  of  an 
inch  in  diameter,  and  one  and  a  half  inches  long,  is  securely  at- 
tached, perpendicularly,  to  the  palatal  surface,  and  the  whole 
surrounded  with  plaster  to  the  depth  of  one  inch.  Thus  will  be 
constituted  two  sections,  which  are  separated,  and  the  wax  washed 
out.     The  external  ends  of  the  channels,  formed  by  the  pencils, 


CAST    METAL    BASE. 


625 


are  then  countersunk,  and  into  each  is  inserted  a  wax  cone,  the 
one  forming  a  pouring-gaine  and  the  other  a  waste  pocket.    The 


Fig.  572. 


-„.S 


latter  should  be  entirely  covered   by  the  plaster.    The  whole  is 
now  invested  in  the  repair  flask,  and  subsequently  submitted  to 

the  process  of  drying. 
40 


626  MECHANICAL    DENTISTRY. 

Dr.  W.  S.  Elliott,  of  New  York,  has  taken  adv^antage  of  the 
method  above  described  to  overcome  the  difficulties  attending 
the  construction  of  continuous-gum  work. 

To  maintain  a  perfect  adaptation  of  a  swaged  plate  seems 
almost  impossible,  in  consequence  of  the  springing  of  the  plate 
in  the  furnace.  To  avoid  this  difficulty,  the  following  plan  is 
suggested  :  The  plaster  model  is  first  covered  with  two  thick- 
nesses of  French  flower  wax,  carefully  adjusted.  From  this  a 
metallic  die  and  counter-die  are  made,  and  a  very  thin  (No.  32) 
platina  plate  is  swaged  to  fit  the  waxed  model.  The  labial 
border  need  not  be  returned,  as  in  ordinary  cases.  Upon  this  the 
teeth  are  arranged,  and  the  case  is  transferred  to  the  furnace  for 
biscuiting  and  enameling.  After  proper  annealing,  it  is  replaced 
upon  the  model  and  waxed  up,  on  the  labial  and  buccal  borders, 
over  the  edge  of  the  plate,  then  flasked,  the  wax  removed,  and 
the  metal  cast  upon  it  in  the  manner  heretofore  described. 

Danger  of  checking  the  enamel  is  associated  WMth  the  process  ; 
but  success  has  attended  the  effort,  and  it  is  hoped  that  further 
experiments  will  insure  perfect  and  uniform  results. 


CHAPTER  XVII. 

DEFECTS    OF    THE    PALATAL    ORGANS    AND    THEIR    TREAT- 
MENT BY  ARTIFICL\L  MEANS. 

Palatine  Defects. — Defects  of  the  palatine  organs  may  be 
divided  into  two  classes,  viz.,  accidental  and  congenital.  The 
first  includes  all  loss  of  substance  in  either  hard  or  soft  palate  by 
disease  or  otherwise.  Such  defects  are  not  uniform  in  locality 
or  extent,  being  sometimes  but  a  simple  perforation  of  the  palate, 
and  at  others  involving  the  destruction  of  the  entire  soft  palate 
a  considerable  portion  of  the  hard  palate,  the  vomer  and  turbin- 
ated bones,  and  the  loss  of  the  teeth. 

The  second  class  includes  all  malformations,  from  the  simple 
division  of  the  uvula  to  an  opening  through  the  velum,  palatine 
and  maxillary  bones,  and  a  division  of  the  upper  lip,  thus  unit- 
ing throughout  their  entire  extent  the  nasal  passages  with  the 
oral  cavity. 

These  malformations  are  quite  similar  in  character,  but  not  uni- 
form in  extent.  They  may  be  said  to  begin  with  the  uvula,  and  in 
the  uvula  and  velum  always  occupy  the  median  line  ;  but  as  the 
defect  progresses  anteriorly,  it  may  deflect  to  one  side  or  the 
other  of  the  vomer,  and  follow  the  nasal  passage  through  the 
lips,  leaving  the  vomer  articulated  with  the  palate  bone  on  one 
side  ;  while  in  other  cases  the  deformity  seems  to  follow  the 
median  line,  and  thus  involves  both  nasal  passages  and  termi- 
nates in  a  double  fissure  of  the  lip. 

In  both  classes  (accidental  and  congenital)  the  faculty  of  dis- 
tinct articulate  speech  is  seriously  impaired  by  defects  of  any 
extent.  In  ordinary  cases  of  congenital  deformity,  deglutition  is 
not  materially  interfered  with.  The  patient,  having  never 
known  any  other  method  of  swallowing,  is  not  conscious  of  any 
difficulty.  Accidental  lesions,  however,  coming  generally  in 
adult   life,  produce,  in    this    respect,   very  great  inconvenience. 

627 


628  .  MECHANICAL    DENTISTRY. 

The  remedy  for  these  evils  must  be  the  closing  of  the  abnormal 
passage  by  some  means  which  will  restore  the  functions  to  the 
deformed  organs.  In  perforations  of  the  hard  palate,  unless  of 
extraordinary  extent,  the  method  is  very  simple.  In  the  loss  of 
the  soft  palate  by  disease  the  remedy  is  more  difficult,  and  in 
extensive  congenital  deformity  still  more  complicated  appliances 
will  be  required. 

As  we  have  classified  the  defects,  we  shall  also  classify  the  ap- 
pliances used  for  their  remedy. 

The  term  obturator  will  be  used  for  all  appliances  intended  to 
stop  a  passage,  or  all  openings  in  the  hard  or  soft  palate  which 
have  a  complete  boundary.  Appliances  made  to  supply  the  loss 
of  the  posterior  soft  palate,  whether  accidental  or  congenital, 
will  be  called  artificial  vela,  or  palates. 

Obturators. — Any  unnatural  opening  from  the  oral  cavity 
into  the  nasal  cavity,  which  will  permit  the  free  passage  of  the 
breath,  will  impair  articulation.  Any  appliance  which  will  close 
such  passage,  and  can  be  worn  without  inconvenience,  will  re- 
store articulation.*  Obturators  were  formerly  made  of  metallic 
plate,  gold  or  silver  being  most  commonly  employed,  and  many 
very  ingenious  pieces  of  mechanism  were  the  result  of  such 
efforts,  but  latterly  vulcanized  rubber  has  almost  entirely  super- 
seded the  use  of  metals.  Vulcanite  has  been  found  preferable 
to  metals,  being  much  lighter  and  much  more  easily  formed  and 
adapted,  particularly  when  of  peculiar  shape. 

The  steps  to  be  taken  in  the  formation  of  an  obturator  are  not 
unlike  those  used  in  making  a  base  for  artificial  teeth.  It  is  es- 
sential that  an  accurate  model  be  obtained  of  the  opening,  the 
adjacent  palatal  surface,  and  the  teeth,  if  any  remain  in  the  jaw. 
For  this  purpose  an  impression  in  plaster  is  the  only  reliable 
means  for  such  an  end.  Care  must  be  used  that  a  surplus  of 
plaster  is  not  forced  through  the  opening,  thus  preventing  the 
withdrawal  of  the  impression  by  an  accumulated  and  hardened 

*The  student  will  bear  in  mind  that  no  cognizance  is  here  taken  of  openings  similar 
to  those  described  in  cases  of  congenital  fissure,  where  the  surgeon  has  united  the 
soft  palate,  and  left  an  opening  through  the  hard  palate,  to  be  covered  by  an  obtura- 
tor. In  such  cases,  neither  the  surgeon's  operation  nor  the  obturator  will  prove  of  any 
material  advantage. 


ARTIFICIAL    TREATMENT    OF    PALATAL    DEFECTS.  629 

mass  larger  than  the  opening  through  which  it  passed.  To 
avoid  this,  beginners  or  timid  operators  had  better  take  an  im- 
pression in  the  usual  manner  with  wax  ;•  if  this  is  forced  through, 
it  can  be  easily  removed,  without  injury  to  the  patient.  From 
this  wax  impression  make  a  plaster  model,  and  upon  this 
form  an  impression- cup  of  sheet  gutta-percha,  with  a  stick, 
piece  of  wire,  strip  of  metal,  or  any  other  convenient  thing 
for  a  handle.  This  extemporized  impression-cup  must  not  im- 
pinge upon  the  borders  of  the  opening,  neither  should  it  enter 
to  any  extent.  With  a  uniform  film  of  soft  plaster  of  from  one- 
sixteenth  to  one-eighth  of  an  inch  in  thickness  laid  over  this 
cup,  a  correct  impression  can  be  made  without  any  surplus  to 
give  anxiety.  Upon  a  correct  plaster  cast,  taken  from  such  an 
impression,  make  a  model  of  the  obturator  out  of  gutta-percha, 
thin  sheets  of  modeling  compound,  or  other  plastic  substance ; 
the  subsequent  steps  being  in  principle  the  same  as  in  making 
any  other  piece  of  vulcanite.  It  is  desirable  that  it  should  enter 
the  perforation  and  restore  as  far  as  possible  the  lost  portion 
of  the  palate,  but  it  must  not  protrude  into  or  in  any  way  obstruct 
the  nasal  passage. 

The  entire  freedom  of  the  nasal  passage  is  essential  to  the 
purit}^  of  articulation. 

That  portion  of  the  obturator  which  occupies  the  oral  cavity 
should  be  made  as  delicate  as  possible,  consistent  with  its 
strength  and  durability. 

A  clumsy  contrivance  will  interfere  with  articulation  almost 
as  much  as  it  is  improved  by  stopping  the  opening  ;  therefore, 
if  the  obturator  could  be  confined  entirely  to  the  opening,  like 
a  cork  in  a  bottle,  it  would  be  all  the  more  desirable,  but  as  it 
cannot,  resort  must  be  made  to  clasping  to  the  contiguous  teeth, 
if  there  are  any,  and  if  not,  the  obturator  must  spread  out  over 
the  whole  jaw,  and  receive  its  support  in  the  same  manner  as 
would  a  set  of  artificial  teeth.  In  fact,  this  is  just  what  it  would 
become  in  such  a  case,  viz.,  an  upper  set  of  teeth  bridging  over 
and  filling  up  an  opening  in  the  palate,  thus  combining  an  ob- 
turator with  a  set  of  teeth. 

Kingsley's  Obturators  and  Methods  of  Procedure. — 
The    following    descriptions,    with    accompanying    illustrations. 


630  MECHANICAL    DENTISTRY. 

were  contributed  to  this  work  by  Professor  Norman  W. 
Kingsley,  who  excels  in  the  practice  of  this  difficult  and  im- 
portant specialty  of  the  Dental  Art.  The  doctor  writes  as  fol- 
lows : — 

Fig.  574  represents  an  obturator  without  teeth  and  without 
clasps,  for  a  perforation  of  the  hard  palate,  being  sustained  in  situ 
by  impinging  upon  the  natural  teeth  with  which  it  comes  it  con- 
tact. Accuracy  of  adaptation  and  delicacy  in  form  are  ail  that  is 
essential  in  such  cases,  and  the  restoration  of  the  speech  will 
follow  immediately. 

Fig.  575  represents  a  more  complicated  obturator,  adapted  to 
an  opening  in  the  soft  palate. 

The  necessity  for  a  variation  in  the  plan  will   be  found  in  the 

Fig.  574.  Fig.  575. 


1% 


anatomical  fact  of  the  constant  muscular  action  of  the  soft  palate, 
which  would  not  permit,  without  irritation,  the  presence  of  an 
immovable  fixture. 

This  is  contrived,  therefore,  with  a  joint  that  will  permit  the 
part  attached  to  the  teeth  to  remain  stationary,  while  the  obtura- 
tor proper  is  carried  up  or  down  as  moved  by  the  muscles.  The 
joint.  A,  should  occupy  the  position  of  the  junction  of  the  hard 
and  soft  palates.  The  joint  and  principal  part  of  the  appliance 
is  made  of  gold,  the  obturator  of  vulcanite.  The  projection,  i>, 
lies  like  a  flange  upon  the  superior  surface  of  the  palate  and 
sustains  it ;  otherwise  the  mobility  of  the  joint  would  allow  it 
to  drop  out  of  the  opening.  This  flange  is  better  seen  in  the  side 
view  marked  C.  It  is  readily  placed  in  position  by  entering  the 
obturator  first,  and  carrying  the  clasps  to  the  teeth  subsequently. 


ARTIFICIAL    TREATMENT    OF    PALATAL    DEFECTS.  63 1 

Figures  574  and  575  will  illustrate  the  essential  principles  in- 
volved in  all  obturators.  The  ingenuity  of  the  dentist  will  often 
be  taxed  in  their  application,  as  the  cases  requiring  such  appli- 
ances all  vary  in  form  and  magnitude. 

Artificial  Palates. — Before  proceeding  to  a  description  of 
appliances,  a  brief  reference  to  the  anatomical  relations  and  func- 
tions of  the  palate  will  be  necessary.  The  palate  exercises  quite 
as  important  an  office  in  the  articulation  of  the  voice  as  does  the 
tongue  or  lips.  Being  a  muscular  and  movable  partition  to  sep- 
arate the  nasal  and  oral  cavities,  one  edge  is  attached  to  the 
border  of  the  hard  palate,  while  the  other  vibrates  between  the 
pharynx  and  the  tongue.  The  voice,  therefore,  as  it  issues  from 
the  larynx,  is  directed  by  the  palate  entirely  into  the  mouth,  or 
through  the  nose,  or  permitted  to  pass  both  ways. 

A  very  slight  deviation  in  this  organ  from  its  natural  form 
will  make  the  voice  give  a  different  sound.  So  will,  also,  the  pres- 
ence of  anything  that  clogs  the  natural  passages,  either  oral  or 
nasal. 

Place  any  obstruction  in  the  nasal  passages,  paralyze  the  soft 
palate,  or  let  it  be  deficient  in  size,  and  the  power  of  distinct 
articulation  is  wanting. 

The  evidence  of  this  statement  is  frequently  found  after  the 
surgeon  has  successfully  performed  the  operation  of  staphylor- 
raphy  in  cases  of  congenital  fissure. 

In  such  instances  (with  rare  exceptions)  the  newly-formed 
palate  is  so  deficient  in  length,  and  so  tense,  as  to  be  deprived  of 
its  function.  It  cannot  be  raised  so  as  to  meet  the  pharynx  and 
shut  off  the  nasal  passage,  but  hangs  like  an  immovable  septum 
to  divide  the  column  of  sound. 

F'g-  576  represents  a  defective  palate  belonging  to  the  first 
class,  the  uvula  and  a  portion  of  the  soft  palate  contiguous  be- 
ing destroyed  by  disease.  In  such  a  case  an  obturator  would  be 
useless  ;  the  constant  activity  and  the  surrounding  parts  would 
not  tolerate  it.  The  material  used  for  a  substitute  must  be  soft, 
flexible,  and  elastic,  and  the  elastic  vulcanite  is  admirably  adapted 
to  this  purpose. 

By  observing  the  cut  (Fig.  576)  it  will  be  seen  that  a  portion 
of  the  soft  palate  along  the  median  line  remains,  and  consequently 


632 


MECHANICAL    DENTISTRY. 


there  will  be  considerable  muscular  movement  which  must  be 
provided  for,  and  which  may  be  taken  advantage  of.  It  is  desira- 
ble to  make  this  movement  available  in  using  an  artificial  palate, 
as  thereby  more  delicate  sounds  are  produced  than  otherwise. 

This  case  presents  some  extraordinary  difficulties  in  the  fact 
that  all  the  teeth  of  the  upper  jaw  have  been  extracted,  and  it 
was  necessary,  therefore,  to  adapt  a  plate  which  should  not  only 
sustain  teeth  for  mastication,  but  bear  the  additional  responsi- 
bility of  supporting  the  artificial  palate.  In  the  choice  of  mate- 
rial best  adapted  for  the  base  for  the  teeth   in   such   instances,  it 

Fig.  576. 


is  preferable  to  adopt  that  which  will  prove  the  most  durable. 
There  are  too  many  interests  involved  to  risk  the  adoption  of 
anything  but  the  best.  In  the  case  under  description,  the  patient 
desired  duplicates,  and  two  sets  of  teeth  were  made,  one  on  gold 
and  the  other  on  platina  with  continuous  gum. 

The  plates  were  made  like  other  sets  of  teeth,  with  the  excep- 
tion of  a  groove  located  on  the  median  line  at  the  posterior  edge 
to  receive  the  attachment  for  the  palate  (marked  C,  in  Fig.  577). 

Fig.  577  will  indicate  the  set  of  teeth  with  palate  attached. 
The  wings  marked  letters  A  and  B  are  made  of  soft  rubber ;  the 
frame  to  support  them  is  made  of  gold,  with  a  joint  to  provide 


ARTIFICIAL   TREATMENT    OF    PALATAL    DEFECTS. 


633 


for  the  perpendicular  motion  of  the  natural  palate,  as  in  the  case 
of  the  obturator  represented  in  Fig.  575. 

When  the  artificial  palate  is  in  use,  the  joint  and  frame  imme- 
diately contiguous  lie  close  to  the  roof  of  the  mouth  ;  the  rubber 
wing,  letter  A,  bridges  across  the  opening  on  the  inferior  sur- 
face or  side  next  the  tongue ;  the  wing,  letter  B,  bridges  across 
the  opening  on  the  superior  or  nasal  surface,  and  is  also  pro- 
longed backward  until  it  nearly  touches  the  muscles  of  the 
pharynx  when  they  are  in  repose. 

Both  these  wings  reach  beyond  the  boundary  of  the  opening 
and  rest  on  the  surface  of  the  soft  palate  for  a  distance  of  from 
one-eighth  to  one-quarter  of  an  inch,  thus  embracing  the  entire 
free  edge  of  the  soft  palate.     This  last  provision   enables   the 

Fig.  577. 


natural  palate  to  carry  the  artificial  palate  up  or  down,  as  articu- 
lation may  require. 

When  the  organs  of  speech  are  in  repose,  there  is  an  opening 
behind  the  palate  sufficient  for  respiration  through  the  nares. 
When  these  organs  are  in  action,  a  slight  elevation  of  the  palate, 
or  a  contraction  of  the  pharynx,  will  entirely  close  the  nasal  pas- 
sage and  direct  all  the  voice  through  the  mouth.  The  palate 
thus  becomes  a  valve  to  open  or  close  the  nares,  and  to  be 
tolerated  must  be  made  with  thin  and  delicate  edges  which  will 
yield  upon  pressure.  An  instrument  thus  made  will  restore,  as 
far  as  is  possible  by  mechanism,  the  functions  of  the  natural 
organ. 

In  the  case   under  description,   the  patient  was  a  lady;  the 


634  MECHANICAL    DENTISTRY. 

defect  had  existed  for  seven  years  before  remedy.  Articulation 
was  very  defective ;  distinct  and  perfect  articulation  followed 
within  one  month. 

Fig.  578  represents  the  artificial  palate  separated  into  its  con- 
stituent parts.  The  frame  is  bent  at  the  joint,  in  the  engraving, 
to  show  a  stop,  marked  D,  which  prevents  the  appliance  from 
dropping  out  of  position.  Letter  C  shows  the  tongue,  which 
enters  the  groove  in  the  plate  of  teeth  and  connects  them.  Let- 
ters A  and  B  are  the  rubber  flaps,  which  are  secured  to  the 
frame  by  the  hooks  as  seen  in  the  engraving. 

The  process  for  making  the  rubber  wings  will  be  found  de- 
scribed on  page  640. 

Fig.  579  shows  a  more  extensive  palatine   defect   of  the  first 

Fig.  578. 


class.  In  this  case  the  entire  soft  palate  is  gone,  together  with 
a  small  portion  of  the  hard  palate  at  the  median  line. 

Although  this  defect  is  greater  in  extent,  the  means  for  its 
remedy  are  more  simple.  The  muscles  of  the  palate  are  entirely 
gone,  and  consequently  no  perpendicular  movement  need  be 
provided  for. 

The  appliance  in  this  case  will  resemble  an  elastic  obturator 
more  than  the  valve-like  palate  of  the  preceding  one.  The 
principle  here  adopted  will  be  substantially  that  recommended 
by  Mr.  Sercombe,  of  London,  some  ten  years  since,  and  con- 
sists of  a  plate  with  a  set  of  teeth  in  the  usual  form,  and  attached 
to  its  posterior  edge  an  apron  of  soft  rubber,  which  shall  bridge 
the  opening  on  its  inferior  surface,  extending  nearly  to  the 
pharynx.     Fig.  580  represents  the  set  of  teeth   with  the   palate 


ARTIFICIAL  TREATMENT  OF  PALATAL  DEFECTS. 


635 


attached.  In  Mr.  Sercombe's  appliance  this  apron  was  made  of 
the  common  sheet  rubber  in  the  market,  prepared  for  other 
uses,  and  is  objectionable  for  two  reasons  :  ist,  a  want  of 
purity  in  the  materials  of  which  it  is  compounded,  in  many  in- 
stances substances  being  used  in  its  manufacture  which  would 
prove  deleterious  to  the  health  of  the  patient ;  and,  2d,  its  uni- 
formity of  thickness.  It  is  far  preferable,  therefore,  to  make  a 
mold  which  will  produce  a  palate  of  pure  and  harmless  materials, 
and  which  shall  be  of  sufficient  thickness  in  the  central  part, 
and  at  its  anterior  edge,  to  give  it  stability,  and  shall  have  a  thin 

Fig.  579. 


and  delicate  boundary  wherever  it  comes  in  contact  with 
movable^tissue.  Such  a  palate  may  be  made  in  a  mold  by  sub- 
stantially the  same  process  as  hereinafter  described.  (See  page 
640.)  It  may  be  secured  to  the  plate  by  a  variety  of  simple 
means.  One,  which  will  give  as  little  trouble  to  the  patient  as 
any  other,  is  to  make  a  series  of  small  holes  along  the  edge  of 
the  plate  and  stitch  it  on  with  silk,  or  fine  platina,  gold,  or  silver 
wire  may  be  used. 

It  is  desirable  to  have  the  plate  and  palate  present   a  uniform 
surface  on   the  lingual  side.     In   fitting  the  plate,  therefore,  it 


636 


MECHANICAL    DENTISTRY. 


may  be  raised  along  the  posterior  edge  from  the  sixteenth  to  the 
tenth  of  an  inch,  according  to  the  thickness  of  palate  desired. 
The  rubber  will  thus  be  placed  on  the  palatine  surface  of  the 
plate  and  present  uniformity  on  the  lingual  surface. 

A  little  thought  will  show  that  in  this  case  the  patient  must 
educate  the  imiscles  of  the  pharynx  alone  to  do  the  work  of  shut- 
ting off  the  nares,  which  in  the  former  case  Avas  performed  by 
them  in  conjunction  with  the  muscles  of  the  palate.  Perfection 
of  articulation  will  therefore  depend  upon  the  success  of  the 
patient  in  this  new  use  of  these  muscles. 

In  cases  of  accidental  lesions  of  the  palate,  such  as  are  under 

Fin.  5S0. 


consideration,  this  education  of  the  muscles  to  a  new  work  will 
not  be  difficult.  The  patient  at  some  former  time  has  had  the 
power  of  distinct  articulation  ;  his  ear  has  recognized  in  his  own 
voice  the  contrast  between  his  present  and  former  condition  ;  the 
ear  will  therefore  direct  and  criticise  the  practice  until  the  result 
is  attained. 

In  the  case  illustrated  by  Figs.  579  and  580,  the  defect  had 
existed  for  twenty-eight  years,  the  patient  at  the  time  of  the 
introduction  of  the  artificial  palate  being  nearly  fifty  years  of 
age.  The  effect  upon  the  speech  was  instantaneous.  Articu- 
lation was  immediately  nearly  as  distinct  as   in  youth,  and  this 


ARTIFICIAL    TREATMENT    OF    PALATAL    DEFECTS.  637 

remarkable  distinctness  can  only  be  accounted  for  upon  the  as- 
sumption that  the  pharyngeal  muscles  had  undergone  a 
thorough  training  in  the  vain  effort  to  articulate  without  any 
palate.* 

The  two  cases  chosen  to  illustrate  the  application  of  artificial 
palates  in  accidental  lesion  have  required,  as  will  have  been  per- 
ceived, entire  upper  sets  of  artificial  teeth  in  connection  with 
the  palates.  This  selection  was  purposely  made,  because  the 
difficulties  to  be  overcome  are  much  greater.  In  cases  where 
there  are  natural  teeth  remaining  in  the  upper  jaw,  the  palate 
and  its  connection  with  a  plate  would  be  substantially  the  same, 
and  the  plate  might  easily  be  secured  to  the  teeth  by  clasps,  in 
the  same  manner  as  a  partial  denture. 

Artificial  Palates  for  Congenital  Fissure. — Congenital 
fissure  of  the  palate  presents  far  greater  difficulties  to  be  over- 
come than  cases  of  accidental  lesion.  The  opening  is  commonly 
more  extensive,  the  appliance  more  complicated,  and  the  result 
more  problematical.  Nevertheless,  appliances  have  been  made 
in  a  large  number  of,  cases,  which  have  enabled  the  wearer  to 
articulate  with  entire  distinctness,  so  much  so  as  not  in  the  least 
to  betray  the  defect.  The  first  efforts  in  this  direction  were  of 
the  character  of  obturators,  simply  plugs  to  close  the  posterior 
nares,  and  the  results  were  far  from  satisfactory.  It  was  not 
until  it  was  recognized  that  the  two  classes  of  cases  (accidental 
and  congenital)  were  entirely  distinct  that  much  progress  was 
made. 

Nearly  every  case  of  accidental  lesion  can  be  treated  with  an 
obturator  with  considerable  success;  very  rarely  will  an  obtura- 
tor be  of  any  benefit  in  congenital  fissure,  even  if  the  congenital 
and  accidental  case  present  substantially  the  same  form  of  open- 
ing. For  this  reason  so  much  mystification  has  been  thrown 
around  these  appliances  within  a  few  years  past.  The  character 
of  the  different  classes  has  been  confounded,  and  an  instrument 
admirably  adapted  to  one  class  has  had  claimed  for  it  an  equal 
application  to  the  other  class.     Let  it  be  understood,  therefore. 


*  An  account  of  this  case  appears  in  the   Argtis,  of  flainbridge,  Georgia,  August 
I,  1868,  written  by  the  patient  himself,  the  editor  of  that  paper. 


638 


MECHANICAL    DENTISTRY. 


as  a  rule  to  which  there  will  be  but  few  exceptions,  that  congeni- 
tal fissure  of  the  soft  palate  requires  for  its  successful  remedy  a 
soft,  elastic,  and  movable  appliance,  and  that  when  the  most 
skilfully  made  and  adapted  instrument  is  worn,  articulation  must 
be  learned,  like  any  other  accomplishment.  Various  inventions 
have  been  made  for  this  purpose  within  the  last  twenty-five 
years,  from  the  most  complicated  one  of  Mr.  Stearns,  described 
in  the  first  edition  of  this  work,  to  the  extreme  of  simplicity  of 
bridging  the  gap  with  a  simple  flap  of  rubber.  The  .Stearns  in- 
strument, with  all  its  complexity,  embodied  the  only  true  prin- 


ciple, viz.,  the  rendering  available  the  muscles  of  the  natural 
palate  to  control  the  movements  of  the  artificial  palate. 

The  essential  requisites  of  an  artificial  palate  will  be  to  restore, 
as  far  as  possible,  the  natural  form  to  the  defective  organs  with 
such  material  as  shall  restore  their  functions.  Muscular  power, 
certainly,  cannot  be  given  to  a  piece  of  mechanism,  but  the  ma- 
terial and  form  may  be  such  that  it  will  yield  to  and  be  under 
the  control  of  the  muscles  surrounding  it,  and  thus  measurably 
bestow  upon  it  the  function  of  the  organ  which  it  represents. 

Fig.  581  represents  a  model  of  a  fissured  palate,  complicated 
with  hare-lip  on  the  left  side  of  the  mesial  line.     There  is  a  divi- 


ARTIFICIAL   TREATMENT    OF    PALATAL    DEFECTS. 


639 


sion,  also,  of  the  maxiHa  and  the  alveolar  process,  the  sides 
being  covered  with  mucous  membrane,  which  come  in  contact 
with  each  other  but  are  not  united.  The  left  lateral  incisor  and 
left  canine  tooth  are  not  developed. 

Fig.  582  represents  the  artificial  velum,  as  viewed  from  its 
superior  surface,  together  with  the  attachment  and  two  artificial 
teeth  to  fill  the  vacancy. 

The  lettered  portion  of  this  appliance  is  made  of  elastic  vul- 
canized rubber ;  its  attachment  to  the  teeth  of  hard  vulcanized 
rubber,  to  which  the  velum  is  connected  by  a  stout  gold  pin 
firmly  embedded  at  one  end  in  the  hard  rubber  plate.  The  other 
end  has  a  head,  marked  C,  which,  being  considerably  larger  than 
the  pin,  and  also  the  corresponding  hole  in  the  velum,  it  is  forced 
through, — the  elasticity  of  the  velum  permitting, — and  the  two 
are  securely  connected. 

Fig.  582. 


The  process,  B,  laps  over  the  superior  surface  of  the  maxilla 
(the  floor  of  the  naris),  and  effectually  prevents  all  inclination  to 
droop. 

The  wings,  A  A,  reach  across  the  pharnyx,  at  the  base  of  the 
chamber  of  the  pharnyx,  behind  the  remnant  of  the  natural 
velum. 

The  wings,  D  D,  rest  upon  the  opposite  or  anterior  surface  of 
the  soft  palate. 

Fig.  583  represents  a  model,  the  same  as  Fig.  581,  with  the 
appliance,  Fig.  582,  in  situ. 

The  wing,  D  D,  in  Fig.  582,  and  the  posterior  end  of  the  arti- 
ficial velum  only  in  this  cut  being  visible. 

Method  of  Making  an  Artificial  Palate. — The    success   of 


640 


MECHANICAL    DENTISTRY. 


these  appliances  depends   very  much  upon  the   accuracy  of  the 
model  obtained  to  work  by. 

It  is  essential  that  the  entire  border  of  the  fissure  from  the 
apex  to  the  uvula  should  be  perfectly  represented  in  the  model, 
as  the  parts  are  when  in  repose.  It  is  also  necessary  that  the 
model  show  definitely  the  form  of  the  cavity  above,  and  on 
either  side  of  the  opening  through  the  hard  palate,  being  that 
part  of  the  cavity  which  is  hidden  from  the  eye.  It  is  desirable, 
also,  that  the  posterior  surface  of  the  remains  of  the  soft  palate 
be  shown,  but  this  is  not  essential  ;  but  it  is  especially  important 


that  the  anterior  or  under  surface  be  represented  with  relaxed 
muscles  and  in  perfect  repose.  The  impression  for  such  a  model 
must  be  taken  in  plaster  ;  it  is  the  only  material  now  in  use 
adapted  to  the  purpose.  An  ordinary  Britannia  impression-cup 
may  be  used,  selecting  one  in  size  and  form  corresponding  to  the 
general  contour  of  the  jaw.  This  cup  will  be  found  too  short  at 
the  posterior  edge  to  receive  the  soft  palate,  but  it  may  be  ex- 
tended by  the  addition  of  a  piece  of  sheet  gutta-percha,  which 
must  be  molded  into  such  form  as  not  to  impinge  upon  the  soft 
palate,  but  which  will  reach  under  and  beyond  the  uvula,  and 
thus  protect  the  throat  from  the   droppings  of  plaster.     Before 


ARTIFICIAL   TREATMENT    OF    PALATAL    DEFECTS.  64 1 

using  the  plaster  the  posterior  edge  of  the  gutta-percha  exten- 
sion may  be  softened  by  heat  and  introduced  into  the  mouth  ; 
contact  with  the  soft  palate  will  cause  it  to  yield,  so  that  there  is 
no  danger  of  its  forcing  away  the  soft  tissues  when  the  plaster  is 
used.  With  the  precaution  not  to  use  too  much  plaster,  the  first 
effort  will  be  to  get  only  the  lingual  surface.  After  trial,  if  the 
impression  show  definitely  the  entire  border  of  the  fissure,  and 
the  soft  palate  has  not  been  pushed  up  by  contact  with  the  cup, 
nor  pulled  up  by  the  spasmodic  action  of  the  levator  muscles,  it 
is  all  that  is  thus  far  desired.  If,  however,  the  soft  parts  have  been 
disturbed  (which  on  close  comparison  a  little  experience  will 
decide),  it  is  better  to  cast  a  model  into  the  impression,  and  upon 
this  model  extemporize  an  impression-cup  as  described  on  page 
629.  This  temporary  cup  will  have  the  advantage  of  the  former, 
insomuch  that  it  will  require  but  a  film  of  plaster  to  accomplish 
the  result,  thus  lessening  the  danger  of  disturbing  the  soft  tis- 
sues. After  the  removal,  if  it  is  seen  that  any  surplus  has  pro- 
jected through  the  fissure  and  lapped  out  to  the  floor  of  the 
nares,  it  may  be  pared  off. 

The  next  step  will  be  to  obtain,  in  conjunction  with  this  im- 
pression of  the  under  surface,  which  we  will  call  the  palatal  im- 
pression, an  impression  of  the  upper  or  nasal  surface  of  the  hard 
palate. 

This  can  be  done  by  filling  the  cavity  above  the  roof  of  the 
mouth  with  soft  plaster  down  to  the  border  of  the  fissure,  and 
while  yet  very  soft  carrying  immediately  the  palatal  impression 
against  it,  and  retaining  it  in  that  position  until  the  plaster  is 
hard,  which  can  easily  be  ascertained  by  the  remains  in  the  ves- 
sel from  which  it  was  taken.  With  the  precaution  to  paint  the 
surface  of  the  palatal  impression  with  a  solution  of  soap,  to  pre- 
vent the  two  masses  from  adhering  when  brought  in  contact, 
there  will  be  no  difficulty  in  removing  it  from  the  mouth,  leaving 
the  mass  which  forms  the  nasal  portion  in  situ.  With  a  suitable 
pair  of  tweezers  this  mass  is  easily  carried  backward  and  with- 
drawn from  the  mouth,  and  the  irregular  surface  of  contact  indi- 
cates its  relation  to  its  fellow  when  brought  together. 

Fig.  584  will  show  such  an  impression.     The  portion  marked 
A,  B,  C,  will  readily  be  distinguished  as  that  which  entered  the 
41 


642  MECHANICAL    DENTISTRY, 

nasal  cavity.  The  line  of  separation  from  the  palatal  impression 
is  plainly  indicated  in  the  engraving.  The  groove,  marked  D, 
shows  clearly  the  impression  made  by  the  delicate  uvula  in  the 
soft  plaster.  The  nasal  portion  is  relatively  large,  showing  an 
unusually  large  nasal  cavity. 

The  vomer  lies  between  the  projections  marked  A  A,  these 
projections  entering  the  nasal  passages.  The  surfaces  marked  B  B 
come  in  contact  with  the  middle  turbinated  bones,  the  surface 
marked  C  in  contact  with  the  inferior  turbinated  bone.  In  many 
instances  these  turbinated  bones  are  so  large  as  to  nearly  fill  the 
nasal  passages. 

The  method  of  obtaining  the  model  of  the  jaw  from  the  im- 
pression   does     not    require    any    particular    description.      The 

Fig.  584. 


process  is  similar  to  the  making  of  a  cast  into  any  other  mouth 
impression. 

The  model  represented  in  Fig.  581  shows  a  convenient  form 
for  such  a  cast. 

When  the  nasal  portion  of  the  impression  does  not  indicate 
the  superior  surface  of  the  soft  palate,  the  part  may  be  repre- 
sented in  the  cast  by  carving.  It  is  not  essential  to  the  success 
of  the  instrument  to  be  made  that  the  posterior  surface  of  the 
soft  palate  should  be  represented  with  the  same  accuracy  that  is 
required  of  the  inferior  surface,  or  of  both  surfaces  of  the  hard 
palate.  By  the  aid  of  a  small  mirror  and  a  blunt  probe,  the 
thickness  of  the  velum  and  the  depth  behind  the  fissure  can  be 
ascertained  and  the  model  carved  accordingly. 

The  portion  of  the  artificial  palate  coming  in  contact  with  it  is 


ARTIFICIAL    TREATMENT    OF    PALATAL    DEFECTS. 


64: 


SO  elastic  that  it  easily  adapts  itself  to  a  slight  inequality,  ren- 
dering absolute  accuracy  less  important. 

The  next  step  will  be  the  formation  of  a  model' or  pattern  of 
the  palate.  Sheet  gutta-percha  is  preferable  for  this  purpose, 
although  wax,  or  many  other  plastic  substances,  might  answer. 

The  form  which  should  be  given  it  is  better  indicated  by  the 
drawing.  Figs.  582  and  589,  than  a  written  description  would 
give.  The  Stearns  instrument,  of  which  cuts  are  here  given 
(Figs.  585,  586),  was  made  to  embrace  the  edges  of  the  fissure, 
and  was  slit  up  through  the  middle,  so  that  when  the  edges  of 

Fig.  585. 


the  fissure  approach  each  other,  as  they  always  do  in  swallow- 
ing, the  two  halves  of  the  instrument  would  slide  by  each  other, 
and  a  third  flap  or  tongue  was  made  and  supported  by  a  gold 
spring  to  cover  and  keep  closed  this  central  slit.  This  compli- 
cated provision  for  the  contraction  of  the  fissure  is  entirely 
superseded  in  Figs.  582  and  589,  by  making  the  instrument 
somewhat  in  the  form  of  two  lea\^es,  one  to  lie  on  the  inferior 
and  the  other  upon  the  superior  surface  of  the  palate,  and  joined 
together  along  the  median  line.  When  the  fissure  contracts,  the 
halves  of  the  divided  uvula  slide  toward  each  other  between 
these  two  leaves.     The  posterior  portion,  marked  A  in  Fig.  582, 


644 


MECHANICAL    DENTISTRV. 


is  made  very  thin  and  delicate  on  all  its  edges,  as  it  occupies  the 
chamber  of  the  pharynx  and  is  subject  to  constant  muscular 
movement. 

The  sides  are  rolled  slightly  upward  while  the  posterior  end 
is  curved  downward.  The  inferior  portion,  marked  D  D,  in 
Fig.  582,  should  reach  only  to  the  base  of  the  uvula,  and  bridge 
directly  across  the  chasm  at  this  point,  and  no  effort  to  imitate 
the  uvula  should  be  made.  The  extreme  posterior  end  should 
not    reach   the  posterior  wall    of    the  pharynx    when    all    the 

Fig.  586. 


muscles  are  relaxed  by  a  quarter  of  an  inch,  although  subse- 
quent use  must  determine  whether  this  space  be  increased  or 
diminished,  thus  leaving  abundant  room  for  respiration  and  the 
passage  of  nasal  sounds.  In  cases  where  it  is  desirable  to  make 
the  instrument  independent  of  the  teeth,  so  far  as  possible,  in 
its  support,  the  anterior  part,  which  occupies  the  apex  of  the 
fissure  in  the  hard  palate  may  lap  over  on  to  the  floor  of  one  or 
both  nares.  Such  a  projection  is  seen  in  Fig.  582,  marked 
B,  and  a  like  process  is  seen  in  Fig.  589,  but  not  lettered.  Were 
it  not  for  this  process  in  this  case,  the  palate  would   drop   out  of 


ARTIFICIAL   TREATMENT    OF    PALATAL    DEFECTS.  645 

the  fissure  into  the  mouth,  the  single  clasp  at  the  extreme  an- 
terior end  not  being  sufficient  to  keep  the  whole  appliance  in 
place  throughout  its  entire  length.  Caution  must  be  exercised 
that  this  projection  entering  the  nares  be  not  too  large,  or  it 
will  obstruct  the  passage  and  give  a  disagreeable  nasal  tone  to 
the  voice. 

All  these  described  peculiarities  must  be  provided  for  in  the 
gutta-percha  model,  which,  after  having  been  carefully  formed 
to  the  cast,  may  be  tried  in  the  mouth  to  ascertain  its  length  or 
necessary  variations.  When  its  ultimate  form  has  been  decided 
upon,  provision  must  be  made  to  duplicate  it  in  soft  rubber. 

A  parallel  process,  and  one  which  will  be  a  familiar  illus- 
tration, is  used  when  a  set  of  teeth  is  made  on  vulcanite  base. 
A  model  or  pattern  form  is  made  of  gutta-percha,  bearing  the 
teeth,  and  in  all  its  prominent  characteristics  is  shaped  as  the 
completed  denture  is  desired,  the  rubber  duplicate  being  vul- 
canized in  a  plaster  mold.  In  like  manner  the  rubber  duplicate 
of  the  palate,  as  before  described,  may  be  made  in  a  plaster 
mold. 

If  plaster  is  used  it  must  be  worked  with  much  care,  so  that 
the  surface  shall  be  free  from  air  bubbles,  or  the  rubber  palate 
will  be  covered  with  excrescences  that  cannot  be  readily  re- 
moved. By  covering  the  surface  of  the  mold  with  collodion  or 
liquid  silex,  it  will  be  much  improved.  But  ordinarily  plaster 
molds  will  be  found  too  troublesome  for  general  use.  They 
may  be  put  to  a  most  excellent  use,  however,  by  using  one 
to  make  a  duplicate  of  the  gutta-percha  in  hard  rubber. 

This  is  not  necessary  with  those  who  have  had  much  ex- 
perience, but  with  beginners  it  will  be  difficult  to  work  up  the 
gutta-percha  as  nicely  as  may  be  desired  ;  a  duplicate  of  vul- 
canite will  enable  the  operator  to  make  a  more  artistic  model 
of  the  palate,  and  one  which  can  be  handled  with  greater  free- 
dom. 

As  in  the  course  of  a  lifetime  a  considerable  number  of  elastic 
palates  will  be  required,  the  mold  which  produces  them  should 
be  made  of  some  durable  material.  The  type-metal  of  com- 
merce is  admirably  adapted  to  this  use.  The  most  complete 
mold  is  one  made  of  four   pieces,  which    will   produce  a  palate 


646 


MECHANICAL    DENTISTRY. 


of  one  continuous  piece.  Such  a  mold  requires  very  nice 
mechanical  skill  in  fitting  all  the  parts  accurately,  and  unless  the 
operator  has  had  experience  in  such  a  direction,  it  is  better  to 
simplify  the  matter.     By  making  the  palate  in  two  pieces,  to  be 


joined  after  vulcanizing,  the  mold  may  be  made  in  two  pieces, 
and  with  very  little  trouble. 

Fig.  587  shows  a  palate  divided. 

Fig.  588  shows  the  mold  or  flask  in  which  it  is  vulcanized. 
These  flasks  were  made  expressly  for  this  purpose,  but  they  are 

Fig.  5S8. 


not  so  unlike  the  flasks  in  common  use  in  dentists'  laboratories 
that  the  latter  will  not  answer.  The  common  flask  is  simply 
unnecessarily  thick  or  deep. 

The  mold  is  readily  produced  in  the  following  manner  :    Em- 
bed the  two  pieces  of  the  palate   in   plaster,    in   one-half  of  the 


ARTIFICIAL   TREATMENT    OF    PALATAL    DEFECTS.  647 

flask;  when  the  plaster  is  set  and  trimmed  into  form,  duplicate 
it  in  type-metal  by  removing  the  palate,  varnishing  the  surface, 
molding  in  sand,  and  casting.  In  making  the  sand  mold,  take  a 
ring  of  sheet-iron  of  the  same  diameter  of  the  flask  and  three 
or  four  inches  high  ;  slip  it  over  the  flask  and  pack  full  of 
sand.  Separate  them,  remove  the  plaster,  return  the  flask  to 
the  sand  mold,  and  fill  with  the  melted  metal  through  a  hole 
made  in  the  side  or  bottom  of  the  flask.  With  one-half  thus 
made,  substantially  the  same  process  will  produce  the  counter- 
part. 

Fig.  589  shows  the  palate  complete  with  its  attachment  to  the 
teeth.  The  palate  is  secured  to  the  plate  by  a  pin  of  gold  pass- 
ing through  a  hole  in  the  palate  of  the  same  size  ;  the  head  on 
the  pin,  being  larger  than  the  hole,  is  forced  through,  and  thus  the 
two  halves  of  the  paiate  are  bound  together  and  joined  to  the 
plate. 

Fig.  5S9. 


:«*; 


F'fa-  590  shows  a  mold  in  four  pieces.  The  blocks,  C  C,  are 
accurately  adapted  to  the  body  of  the  mold,  marked  A,  and  are 
prevented  from  coming  improperly  in  contact  with  each  other  by 
the  flanges,  D  D,  which  overlap  the  rest  upon  the  sides  of  the 
main  piece.  B  shows  the  top  of  the  mold,  and  the  groove,  E, 
provides  for  the  surplus  rubber  in  packing. 

Such  a  mold  makes  the  most  perfect  appliance  that  can  be  pro- 
duced. The  palate  is  one  homogeneous  and  inseparable  piece. 
The  cut  will  sufficiently  indicate  the  forms  of  the  several  parts. 
Each  of  these  pieces  is  first  made  in  plaster  of  exactly  the  form 
of  which  the  type-metal  is  desired.  They  are  then  molded  in 
sand  and  the  type-metal  cast  as  in  making  an  ordinary  die  for 
swaging.  When  in  use,  a  clamp  similar  to  Fig.  591  is  placed 
around  the  mold  to  keep  the  several  parts  firm  in  their  position. 


648 


MECHANICAL    DENTISTRY. 


The  packing  of  the  mold  with  rubber  will  be  done  in  the  same 
manner  as  when  hard  rubber  is  used  for  teeth  bases,  with  which 
process  it  is  assumed  that  the  operator  is  familiar.     By  washing 

Fig.  590. 


the  surface  of  the  mold  with  a  thick  solution  of  soap  previous 
to  packing,  the  palate  will  be  more  easily  removed  after  vulcan- 
izing. 

The  rubber  used  for  this  purpose  must  be  a  more  elastic  com- 

FiG.  591. 


pound  than  that  used  as  a  base  for  teeth.  The  composition  used 
for  the  elastic  fabrics  of  commerce  will  answer  if  made  of  selected 
materials. 

Suersen's  Obturator. — Dr.  Wilhelm  Suersen,  of  Berlin,  intro- 


ARTIFICIAL    TREATMENT    OF    PALATAL    DEFECTS.  649 

duced  an  obturator  the  principle  of  which  has  seemed  to  many 
the  best  for  obtaining  correct  articulation.  In  describing  it  (in 
American  Journal  of  Dental  Science)  he  says  : — 

"  In  order  to  be  able  to  pronounce  all  letters  distinctly,  it  is 
accordingly  necessary  (besides  other  conditions,  which  are  far 
away  from  our  present  subject)  to  separate  the  cavity  of  the  mouth 
from  the  cavity  of  the  nose  by  means  of  muscular  motion.  That 
separation  is,  under  normal  conditions,  effected,  on  the  one  hand, 
by  the  velum  palati,  which  strains  itself  (consequently  by  the  leva- 
tor and  tensor  palati);  but  on  the  other  hand,  also,  by  a  muscle 
which,  to  my  knowledge,  has,  in  connection  with  these  operations, 
not  yet  received  a  sufficient  amount  of  attention — I  mean  the  con- 
strictor pharyngeus  superior.  This  muscle  contracts  itself  during 
the  utterance  of  every  letter  pronounced  without  a  nasal  sound, 
just  as  the  levator  palati  does.  Theconstrictor  muscle  contracts 
the  cavum  .pharyngo-palatinum,  the  pharynx  wall  bulging  out ; 
and  it  is  chiefly  on  the  action  of  this  muscle  that  I  base  the  sys- 
tem of  my  artificial  palates. 

"  These  palates,  which  in  all  their  parts  are  made  of  hard  caout- 
chouc, consist  of  a  teeth-plate  suitably  attached  to  existing  teeth, 
and  which,  at  the  same  time,  covers  the  fissure  in  the  hard  palate 
(if  such  a  fissure  exists).  Where  the  fissure  commences  in  the 
velum,  that  plate  terminates  in  an  apophysis  broad  enough  for 
filling  up  the  defect.  This  apophysis  is  at  the  same  time  of  such 
thickness  as  to  keep  up  a  contact  between  the  high  edges  form- 
ing the  sides  of  the  apophysis  and  the  two  halves  of  the  velum, 
even  when  the  levator  palati  is  in  activity.  To  bring  about  this 
contact  the  more  surely,  the  high  edges  forming  the  sides  do  not 
rise  straight,  but  obliquely,  toward  the  outside.  The  lower  sur- 
face of  the  apophysis,  turned  toward  the  mouth,  lies  on  about 
an  equal  level  with  the  velum  if  the  latter  is  raised  by  the  levator 
palati.  But  when  the  velum  hangs  loosely  downward  the  back 
part  of  the  artificial  palate  is  lying  over  it.  This  back  part,  ac- 
cordingly, fills  up  the  cavum  pharyngo-palatinum,  and  in  such  a 
manner  as  not  to  impede  the  entrance  of  the  air  into  the  cavity 
of  the  nose  when  the  constrictor  pharyngeus  superior  is  inactive. 
Thus  the  patient  can  without  any  impediment  breathe  through 
the  nose.     But  as  soon  as  the  constrictor  contracts   the    cavum 


650 


MECHANICAL    DENTISTRY. 


pharyngo-palati  (this  happens,  as  I  will  repeat  for  the  sake  of 
clearness,  in  the  utterance  of  every  letter  with  the  exception  of 
1)1  and  //)  the  muscle  already  named  reclines  against  the  vertical 
back  surfaces  of  the  obturator.  By  this  operation  the  air-current 
is  prevented  from  entering  the  cavity  of  the  nose  and  is  com- 
pelled to  take  its  way  through  the  mouth,  and  thus  the  utterance 
loses  its  nasal  sound.  To  the  existence  of  those  vertical  surfaces, 
and  consequently  to  the  thickness  of  that  part  of  my  palates 
which  fills  up  the  fissure  in  the  soft  palate  and  the  cavum  pha- 
ryngo-palatinum,  I  must  attach  special  importance.  But  for 
that  thickness  the  levator  palati,  when  it  rises  upward,  would  not 


p'iG.  592. 


■iG.  593. 


remain  in  contact  with  the  side  edges  of  the  obturator,  nor  would 
the  constrictor  pharyngeus  be  able  to  effect  a  sufficient  termina- 
tion if  the  portion  of  the  obturator  nearest  to  it  consisted  only 
of  a  thin  plate." 

Fig.  592  represents  the  mouth  without  the  apparatus. 

Fig.  593  shows  the  apparatus  in  position ;  Figs.  594  and  595 
give  different  views  of  the  appliance. 

Dr.  Henry  Baker,  in  writing  of  this  appliance  in  the  "  Ameri- 
can System  of  Dentistry,"  says: — 

The  plate,  a,  and  its  narrow  and  thin  apophysis,  /,  which  ex- 
tends from  the  boundary, /;,  of  the  hard  palate  to  the  commence- 
ment of  the  defect,  f,  in  the  soft  palate,  serve  also  as  supporters  to 


ARTIFICIAL  TREATMENT  OF  PALATAL  DEFECTS. 


651 


the  real  thick  obturator,  d.  The  latter  lies  in  the  pharyngo-pala- 
tine  hollow,  so  that  the  lower  surface  of  the  obturator  turned 
toward  the  mouth  is  about  on  the  same  level  as  the  rest  of  the 
velum  palati,  e.  Against  the  vertical  side,/,  and  back  edges, ^,  of 
the  obturator  the  walls  of  the  pharynx  lean  if  the  latter  is  con- 
tracted by  a  contraction  of  the  superior  constrictor  of  the  phar- 
ynx. But  if  the  muscle  just  mentioned  is  not  in  activity,  the 
obturator  does  not  touch  the  pharynx  wall.  The  contraction  of 
the  constrictor  superior  therefore  closes  the  valve  formed,  with 
the  help  of  the  obturator,  between  the  cavity  of  the  mouth 
and  that  of  the  nasal  bone,  while  any  relaxation  of  the  above- 
mentioned  muscle  immediately  reopens  that  valve.     The  thick- 


FiG.  594. 


Fig.  595- 


ness  of  the  obturator  begins  where  the  fissure  in  the  soft  palate 
commences.  With  the  high  side  edges,  of  the  fore  part  of  the 
thick  obturator  (which  edges  ascend,  not  straight,  but  obhquely, 
toward  the  outside),  the  side  halves  of  the  fissured  velum  palati,  r, 
are  in  constant  contact,  even  when  the  latter  are  raised  by  the 
action  of  the  muscular  levator  palati.  The  proportions  of  the 
back  part,  which,  in  the  same  manner  as  in  the  case  of  an 
acquired  defect,  fill  up  the  cavum  pharyngo-palati,  k  k,  are  the 
two  halves  of  the  fissured  uvula. 

Dr.  Suersen  admits  the  importance  of  the  part  taken  by  the 
levator  palati  muscles  in  the  formation  of  articulate  speech  ;  yet 
he  makes  no  provision  for  utilizing  them  as  such,  and  provides 


652  MECHANICAL    DENTISTRY. 

only  for  the  contact  of  the  superior  constrictor  muscle  with  the 
distal  surface  of  the  appliance  to  shut  off  the  nasal  passage.  For 
the  patient  afflicted  with  congenital  cleft  to  acquire  perfect  articu- 
lation with  such  an  appliance  (even  if  it  be  possible)  years  of 
application  and  training  of  this  muscle  would  be  necessary ;  and 
a  little  reflection  will  show  that  this  muscle,  besides  performing 
its  own  functions,  must  be  trained  to  fulfil  those  of  the  velum 
palati,  levator  palati,  and  tensor  palati.  13ut  in  an  accidental 
lesion  this  may  be  all  that  is  necessary,  as  the  patient  having 
previously  learned  to  articulate  distinctly,  and  having  this 
deformity  come  upon  him  afterward,  the  superior  constrictor 
muscle  would  no  doubt  be  sufficiently  developed  to  perform  that 
function.  Sir  William  Ferguson,  in  his  report  of  a  dissection 
made  by  him  of  a  cleft  palate  in  1844,  states  distinctly  that  the 
constrictor  was  very  full,  and  he  also  claimed  for  that  muscle 
very  decided  forward  action  in  deglutition. 

Dr.  Kingsley,  in  speaking  of  Suersen's  appliance,  says : 
"  First,  that  of  all  obturators  this  is  the  best  form  for  congenital 
fissure,  but  while  the  wearer  is  enabled  to  articulate  with  such 
an  instrument,  it  is  only  after  he  has  learned  articulation  with 
another  apparatus.  Second,  that  a  soft,  elastic,  artificial  velum 
is  much  better  adapted  to  the  acquirement  of  articulation  than 
any  unyielding,  non-elastic  substance,  but  when  acquired  an 
obturator  may  be  substituted.  Third,  that  in  very  rare  cases 
articulation  may  be  acquired  with  an  obturator  only,  but  it  is 
the  extra  activity  of  the  pharyngeal  muscles,  while  with  the 
elastic  velum  the  levators  of  the  palate  contribute  largely." 

Baker's  Velum. — Dr.  Henry  Baker  describes  his  appliance 
as  follows  :  "  Numerous  experiments  to  provide  an  artificial 
appliance  with  hard  rubber,  utilizing  the  levator  muscles  to 
control  the  movement  of  the  appliance,  and  with  which  articu- 
lation could  be  learned  as  well  as  with  the  perishable  soft- 
rubber  velum,  resulted  in  my  adoption  of  the  following  device 
in  cases  where  the  cleft  extends  a  little  beyond  the  soft  into 
the  hard  palate,  as  shown  in  Fig.  596.  The  appliance  consists 
of  a  gold  or  hard  rubber  plate  (a.  Fig.  597),  covering  the  roof 
of  the  mouth  down  to  the  junction  of  the  hard  and  soft  palates. 
From    this  point    the    movable   portion,    f,   extends    back   and 


ARTIFICIAL   TREATMENT    OF    PALATAL    DEFECTS. 


653 


downward,  restoring  symmetry  of  the  palatal  surface  by  bridging 
across  and  lying  upon  the  muscles  of  each  side,    c  e  is  a  spring 

Fig.  596. 


The  Cleft;  extending  a  little  beyond  the  soft  into  the  hard  palate. 

controlling  the  upward  movement  of  f.     The   distal   surface,  G, 
or  that  portion  coming  in  contact  with   the   pharyngeal  wall,   is 


Fig.  597. 


f\. 


:  .y 


quite  broad,  and  so  constructed  as   to   articulate  perfectly  with 
this  surface,  while  the  constrictor  muscle   contracts  and   closes 


654 


MECHANICAL    DENTISTRY. 


around  it  on  a  semicircle.     This  is  the   Suersen  principle,  and 
the  main  ideas  are  taken  from  that  appliance. 

The  velum  is  of  polished  hard  rubber,  gold,  or  platinum,  and 
much  resembles  a  chestnut  in  form. 

It  is  attached  to  the  plate  with  a  hinge-joint,  b,  b,  thus  giving 
free  movement  at  the  junction  of  the  hard  and  soft  palates.  At 
the  junction  of  the  hard  and  soft  palates  there  is  a  stop,  which 
prevents  any  downward  pressure  upon  the  muscles  when  in  a 
relaxed  condition. 

Fig.  598. 


Fig.  598  shows  the  appliance  in  position,  the  dotted  lines 
showing  the  part  of  the  appliance  resting  on  the  muscles. 

The  main  advantages  of  this  appliance  are — that  it  is  made  of 
a  durable  material,  is  easily  constructed,  and  that  articulation 
can  be  learned  with  it  more  readily  than  with  any  other  appli- 
ance. In  addition,  it  is  so  easily  movable  as  to  be  acted  upon 
by,  and  be  under  perfect  control  of,  the  muscles  by  which  it  is 
surrounded.  In  studying  the  mechanism  of  speech  we  learn 
that  more  than  three-fourths  of  the  sounds  of  articulate  lan- 
guage depend   upon  the   integrity  of  the  soft   palate  for  their 


ARTIFICIAL  TREATMENT  OF  PALATAL  DEFECTS. 


655 


perfect  enunciation.  This  being  the  fact,  articulation  with  a  rigid 
obturator  must  be  extremely  difficult  to  acquire.  If  three- 
fourths  of   the    sounds  depend    on  the  free    movement   of  the 


Fig.  599. 


\wr^'  f\  \<Sl'^y 


natural  palate,  it  seems  a  sufficient  reason  why  provision  should 
be  made  for  the  same  movement  in  an  artificial  one. 

Dr.  Kingsley  says  that  with  a  yielding  appliance  the  levators 


Fig.  600. 


The  muscles  relaxed,  the  appliance  descended,  thus  giving  a  free  passage  for  nasal 
sounds  and  respiration. 


of  the  palate  contribute  largely  to  correct  speech.  The  surround- 
ing muscles  have  control  over  the  appliance  here  described  in 
the    following  wav :     The  artificial    velum    bridges    across    the 


656  MECHANICAL    DENTISTRY. 

opening  and  lies  upon  the  muscles  of  either  side.  (See  Fig.  59<S, 
D,  D.)  With  all  sounds  requiring  the  closure  of  the  nasal  pas- 
sage it  is  thrown  up  by  the  levator  muscles,  as  shown  at  d  in  the 
sectional  Fig.  599,  there  being  no  resistance.  The  thickness  of 
the  velum  brings  its  posterior  surface  in  close  apposition  with 
the  superior  constrictor  muscle,  f,  affording  in  the  pronunciation 
of  the  gutturals  a  firmer  resistance  to  the  pressure  of  the  tongue, 
G,  than  can  be  obtained  with  a  thin  obturator.  By  the  presence 
of  the  hinge,  b,  the  above  movements  are  rendered  so  free  and 
facile  that  there  is  no  tendeney  to  displacement  of  the  plate, 
such  as  occurs  with  a  rigid  appliance.  If  a  nasal  sound  imme- 
diately follows  a  guttural,  the  descent  of  the  velum  is  rendered 
certain  by  its  own  weight,  even  if  not  aided  by  the  spring. 


NDEX. 


ADHESION,  427 

application  in  retention  of   artificial 
dentures,  430 
Air-chamber,  manner  of  forming,  164 
Allen's  method  of  constructing  continu- 
ous-gum work,  481 
Alloys,  their  general  properties  and  treat- 
ment, and  behavior  in  the  process  of 
compounding,  127 
copper,  121 
gold,  88 

method  of  determining  carat,  94 
converting  into  required  forms, 

97 
lead,  124 
silver,  107 
tin,  125 
platinum,  114 
Aluminum,  117 

alloys  of,  119 
Anatomical  articulator,  Bonwill's,   456 
Antagonizing  model  for  partial  dentures, 
420 

entire  dentures,  453 
upper  dentures,  455 
Anthracite,  26 
Antimony,  125 

Appliances  used  in  generating  and  apply- 
ing heat,  32 
Application  of  continuous  gum  to  partial 
sets,  505 

of  gum  enamels,  484 
Articulators,  456 

Artificial    dentures,  treatment  of    mouth 
preparatory  to,  132 
palates,  631 

for  congenital  fissures,  637 
method  of  making,  639 
Asbestos  molds,  98 
Atmospheric  pressure,  42S 

application  in  retention  of  arti- 
ficial dentures,  430 
Attaching  teeth  to  a  metallic  base  with 
rubber  or  celluloid,  607 

Babbitt  metal,  122 
Bailey's  molding  flask,  170 
Baker's  velum,  652 

42  657 


Baking  furnaces,  56 

Baldwin's     method    of    setting    Logan 

crown,  219 
Base,  cast  metal,  615 
Bath  metal,  122 
Beeswax,  141 
Bell  metal,  122 
"  Best  "  celluloid  heater,  583 
Bismuth,  126 

alloyed,  126 
Bituminous  coals,  23 
Blanks,  celluloid,  579 
Blast  crucible  furnace,  70 
Blowpipes,  36 

mouth,  37 

bellows,  40 

Burgess,  41 

Macomber's,  43 

Fletcher,  44 

gasoline  or  oxy-carbon,  46 

oxy-hydrogen,  48 

Knapp's,  48 
Bonwill's  anatomical  articulator,  456 

method  of  crowning,  201 
Brass,  122 

solder,  122 
Bridge-dentures,  287, 

stationary,  289 

application    to   pulpless    teeth, 

307 
repairing,  308 
Brown's  method,  346 
Darby's  method,  301 
Knapp's  method,  333 
Low's  method,  334 
Melotte's  method,  343 
Register's  method,  313 
Webb's  method,  289 
Williams's  method,  315 
S.  S.  White  Dental    Manufac- 
turing Go's,  system  of,  367 
removable,  350 

Davenport's  method,  364 
Dexter's  method,  350 
Starr's  method,  355 
Parr's  method,  360 
detachable  system,  381 
mandrel  system,  367 


658 


INDEX. 


Britannia  metal,  125 

Brown's  all-porcelain  bridge-denture,  346 

Bunsen  burner,  original,  33 

Burners,  33 

Biittner's  method  of  crowning,  264 

Buxbaum's  dentimeter,  226 


Cannon  Metal,  122 
Caries,  135 

Case's  enamel  cleaver,  224 
Cast  metal  base,  615 
Celluloid  base,  572 

composition    and    manufacture    of, 

573 
facing  to  rubber  base,  601 
formula  for,  574 
heaters,  582 

"  Best,"  583 

"  new  mode,"  591 
metal  casts,  575 
molding,  582 
in  dry  heat,  595 
in  glycerin,  586 
in  hot  moist  air,  582 
in  steam,  588 
plaster  model,  575 
drying  the  cast,  594 
processes    preliminary  to    molding, 

574 

selection  and  preparation  of  blank, 
579;   investing,  577 

waxing  or  modeling,  576 
Charcoal,  23 
Cheoplastic  process,  615 
Clasps,  390 

modifications  in  the  form  of,  395 

plain  band,  395 

scalloped,  397 

standard,  396 

plate  used  in  supplying  loss  of   in- 
ferior molars  and  bicuspids,  400 

annealing  the  plate,  403 

reinforcing,  40I 

adjusting  and  strengthening  projec- 
tions, 404 

modification  in  the  form  of  partial 
plates  for  the  attachment  of,  398 

swaging  plate  retained  by,  402 

unituig  the  plate  and,  405 

vulcanite  plate  attached  to,  562 

partial  or  stay,  398 

Rathburn's  partial  crown  cap,  409 

separation    of   the  teeth  for  the  re- 
ception of,  394 

teeth  suitable  for  the  application  of, 

392 
Cleveland's  air-chamber,  165 
Coal,  bituminous,  23 


Coal,  anthracite,  26 

Coke,  25 

Colored  varnish,  formula  for,  165 

Coloring  materials  for  dental  porcelain, 

474 
Components  of  dental  porcelain,  473 
Continuous-gum  work,  478 

attaching  the  teeth,  481 
jjreparing   and     applying     the 

body, 482 
first  baking,  483 
applying  gum  enamel,  484 
final  baking,  484 
finishing,  repairing,  etc.,  485 
application  to  partial  sets,  505 
Land's  teeth  for,  479 
Allen's  method,  481 
Hunter's  method  and  formulas, 

489 
Haskell's  method,  495 
Field's  method,  499 
Tees'    method     and    formulas, 
502 
Contouring   crowns    constructed   in  sec- 
tions, 279 
Converting    gold    alloys    into    required 

forms,  97 
Coolidge's  steam-gauge,  557 
Copper,  121 
alloys,  121 

with  zinc,  122 
tin,  122 
Counter-die,  metallic,  169  and  177 

progressive,  178 
Crown  or  cap,  gold  caps,  272 
and  bridge-work,  187 
preparation  of  root  for,  190 
excision  of,  191 
porcelain,  192 
Logan,  193 
Brown,  198 
new  Richmond,  199 
Bonwill,  201 
How,  208 
four-pin,  208 
porcelain  dove-tail,  213 

with    gold    collar    attachment, 
217 
Kirk's  method,  218 
Baldwin's  method,  219 
Stowell's  method,  220 
Shulze's  method,  223 
Gates's  method,  215 
Foster's  method,  215 
Howland's  method,  216 
ferrule  or  collar,  224 
Richmond,  224 

method    applied   to  bicus- 
pid roots,  231 


INDEX. 


659 


Crown,  Litch's  method,  233 

Knapp's  process,  241 
Shield's  system,  248 
Lowe's  method,  258 
Biittner's  method,  264 
Matteson's  method,  267 
all  gold,  272 

seamless  contour,  280 

Crucibles,  74 

Defects  of  the  palatal  organs  and  their 

treatment,  627 
Dentimeter  226 

Buxbaum's,  226 

Weirich's,  226 
Dentures,  partial,  187 

entire,  427 
Dexter's  method  of  bridge- work,  350 
Die,  metallic,  169 

preparing  metal  for,  175 

essential  properties  of,  180 

metals  used  in,  185 
Diseased  mucous  membrane  and    gums, 

134 
roots,  treatment  of,  133 
Draft  or  wind  furnace,  54 
Draw-plate,  104 
Duplex  burner,  36 
Dutch  gold,  122 

Elastic  force  of  steam  at  different  tem- 
peratures, 553 
Elements  employed  in  refining  gold,  82 
Enamel  cleaver,  224 
Entire  dentures,  427 

consideration  of  the  principles  and 
attendant  phenomena  involved  in 
the  application  of  the  forces  util- 
ized  as  a  means  of  attachment, 

427  _  _ 

esthetic  requirements  in  the  selection 

and  arrangement  of  the  teeth  of 

replacement,  435 
method  of  overcoming  tendency  to 

change  in  form,  469 
table  of  temperaments,  439 
attached  to  a  swaged  metallic  base- 
plate, 447 
method   of    constructing    base-plate 

for  upper  entire  denture,  447 
method  of  constructing  entire  lower 

denture    mounted    on    a   swaged 

metallic  plate-base,  452 
upper,  modifications  in  the  form  of 

base-plate,  449 
lateral  cavity  plates,  Levett's,  450 
antagonizing  model  for  entire  upper 

and  lower  denture,  453 


Entire  upper  denture,  455 

arranging  and  articulating  the  teeth, 

462 
rimming  the  plate,  464 
constructing    and    attaching     spiral 

springs,  466 
investing,  lining,  soldering,  and  fin- 
ishing the  plate,  467-471 
Essential  properties  of  a  die,  180 
Esthetic   requirements   in   selection   and 

arrangement  of  teeth,  435 
Evans'  vulcanizer,  547 
Extraction,  treatment  after,  135 


Felspar,  473 
Ferrier's  gas  furnace,  68 
Field's   method  of  constructing  continu- 
ous-gum w^ork,  499 
Flashing,  515 
Flasks,  vulcanizing,  522 
Fletcher  automaton,  44 
Forging,  100 

Formulas  for  continuous-gum    body  and 
enamels.  Hunter's,  489 
Tees',  502 
gold  solders,  91 
silver  solders,  11 1 
brass  solder,  122 
soft  solder,  124 
gold  base-plate,  89 
gold  wire,  clasps,  stays,  etc.,  90 
Babbitt  metal,  122 
for    transparent    and    colored    var- 
nishes, 165 
articulating  wax,  415 
celluloid,  574 
Foster's  method  of  crowning,  215 
Fuels,  liquid,  22 
solid,  23 
gaseous,  29 
Furnaces,  draft  or  wind,  54 
baking,  56 
gas,  Land's,  63 
Rollins',  66 
Ferrier's,  68 
Tees',  56 
Liliput's,  56 
gas- crucible,  68 

with  blast,  70 
Fletcher's,  70 
Fusible  alloys,  formulas  for,  185 
table  of,  185 


Gas,  illuminating,  29 
oxy-hydrogen,  31 
crucible  furnace  without  blast,  68 
with  blast,  70 


66o 


INDEX. 


Gas  furnaces,  63 
Gaseous  fuels,  29 
Gasolene,  62 

Gates'  method  of  crowning,  215 
General  properties  of  alloys,  their  treat- 
ment, etc.,  127 
German  silver,  122 
Gold,  geological  situations  of,  75 
properties  of,  76 

influences  of  alloying  on  the  proper- 
ties of,  77 
properties  of  particular  alloys  of,  78 
refining,  82 

elements  employed  in  refining,  82 
separation  of  foreign  metals  from,  83 
alloys  of,  for  dental  purposes,  88 
required  fineness  of  base-plate,  88 
formulas  for  base-plate,  89 
formulas  for  clasps,  stays,  etc.,  90 
solders,  91 
reduction    of,    to    lower    or    higher 

standard  of  fineness,  93 
method  of  ascertaining  carat  of  any 

given  alloy,  94 
reduction  of  to  a  required  carat,  95 
to    raise   from  a  lower  to  a  higher 

carat,  95 
procuring  ingot  of,  97 
forging,  100 

laminating  or  rolling,  loi 
required  thickness  of,  for  base-plate, 

102 
required  thickness  of,  stays,  clasps, 

etc.,  103 
solders,  reduction   of,  into  required 

forms,  103 
wire,  method  of  forming,  104 
spiral  springs,  method  of  construct- 
ing, 105 
alloy  cast  base,  618 
Gongs,  122 


Hand  furnace,  52 

Haskell's  continuous-gum  work,  495 

Hawes'  molding  flask,  172 

Hayes'  vulcanizers,  535 

Heaters,  celluloid,  582 

Heat-generation,  and  application  of,  32 

How's  method  of  crowning,  208 

of  setting  Logan  crown,  193 
Rowland's  method  of  crowning,  216 
Hunter's  continuous-gum  work,  489 
formulas,  489 


Illuminating  gas,  29 
Impressions  of  the  mouth,  138 


Impression  materials,  138 
beeswax,  141 

modeling  composition,  151 
moldine,  151 
plaster-of-Paris,  152 
cups  or  trays,  143 
in  wax  for  partial  upper  dentures, 

142 
partial  lower  dentures,  147 
full  upper  dentures,  148 
full  lower  dentures,  150 
in    ])laster    for    partial    upper    and 

lower  dentures,  154 
for  full  upper  dentures,  158 
lower  dentures,  160 
India  rubber  base-plate  (see  Vulcanized) 
general   properties  of,  508 

compounding    for    dental    purposes, 
510 
Influence  of  alloying  on  the  properties  of 

gold,  77 
Ingot  molds,  97 

laminating,  loi 
Iridium,  115 


Kaolin,  474 

Kingsley's   artificial    velum    and   palate, 

631 

obturators,  629 
Knapp's  stationary  bridge-denture,  333 
method  of  root-crowning,  241 
oxy-hydrogen  blowpipe,  48 


Laminating  or  rolling,  loi 

Lamps,  33 

Land's  continuous  gum  teeth,  479,  512 

gas  furnace,  63 

teeth  for  vulcanite  base,  512 
Lawrence's  steam  gauge,  554 
Lead,  124 

use  in  laboratory,  124 

alloys,  124 
Lewis'  molding  flask,  171 
Litch's  method  of  crowning,  233 
Logan  crown,  193 

LIow's  method  of  setting,  193 

Stowell's  method  of  setting,  220 

Baldwin's  method  of  setting,  219 
Low's  bridge-dentures,  334 

method  of  crowning,  258 


Malleability  of  gold,  77 
Manheim  gold,  122 
Manufacture  of  porcelain  teeth,  475 
Materials  for  impressions,  138 
Matteson's  method  of  crowning,  267 


INDEX, 


66 1 


Melotte  clamp,  53 

Metal  casts   used  in  molding  celluloid, 

575 
Metallic  clasps  attached  to  rubber  plates, 

562 
Metallic   base-plate  with    rubber    attach- 
ment, 607 
Metallic  dies,  169 

counter  dies,  169-177 
Metals,  75 

Method  of  constructing  spiral  springs,  105 
Modeling  composition,  15 1 
Models,  plaster,  161 

Modifications  in  the  form  of  clasps,  395 
Moldine,  151 

Melotte's,  151 
Molding  celluloid,  582 
in  hot  moist  air,  582 
in  glycerin,  586 
in  steam,  588 
in  dry  heat,  595 
flask,  Bailey's,  170 
Lewis',  171 
Hawes',  172 
Molds,  ingot,  97-99 
Mosaic  gold,  122 
Mouth  blowpipe,  37 

Mucous   membrane,  diseased   condition, 
134 


New-Mode  heater,  591 


Obturators,  Kingsley's,  629 

Suersen's,  648 

Baker's,  652 
defiant  gas,  62 
Ottolengui  root  facers,  190 

root  reamer,  192 
Oxy-hydrogen  blow-pipe,  Knapp's,  48 
Oxy-hydrogen  gas,  31 

Palatal  organs,  defects  of,  627 
Palladium,  1 15 
Partial  dentures,  187 

retained  by  clasps,  390 

atmospheric    pressure   or    adhesion 
411 

antagonizing  model  for,  415 

selecting  teeth  for,  417 

arranging  teeth  for,  417 

antagonizing  the  teeth,  420 

investing,  422 

backing,  422 

soldering,  424 

finishing,  424 

vulcanite,  561 
Pinchbeck,  122 


Plaster  models,  161 

from,  an  impression  in   wax,  gutta- 
percha,  or  modeling  composition 
for  partial  dentures,  1 61 
entire  dentures,  163 
from   an   impression    in   plaster   for 

partial  dentures,  165 
entire  dentures,  167 
Plaster-of- Paris,  152 
derivation,  152 
preparation  of,  153 
method  of  hastening  setting,  153 
methods  of  obtaining,  Essig's,  154 
Jack's,  155 
Litch's,  155 
Bennett's,  156 
Dixon's,  156 
Plate  teeth  attached  to  vulcanite  base,  563 
Platinoid  metals,  1 14 
Porcelain  crowns,  192 
teeth,  472 
components  of,  473 
silex,  473 
•   felspar,  473 
kaolin,  474 

coloring  materials,  474 
manufacture  of,  475 
tips,  309 
Preparation  of  root  for  crowning,  190 
Properties  of  gold,  76 
Pulp  canal,  preparation  of,  191 


Rathbun's  supporting  clasps,  409 
Reduction  of  gold  to  a  lower  standard 
of  fineness,  93 

of  gold  solders  to  proper  forms  for 
use,  103 

of  silver  to  required  forms  for  use, 
no 
Reese's  gold  alloy  cast  base,  618 
Refining  gold,  82 

Register's  method  of  bridge-work,  313 
Remarks  on  the  use  of  clasps,  390 
Removable  bridge-dentures,  350 
Removal  of  salivary  calculus,  134 
Repairing  vulcanite  base-plate,  563 
Required  fineness  of  gold  plate,  88 
Rimming  plate,  464 
Rolling  or  laminating,  loi 

mills,  loi 
Rollin's  gas  furnace,  66 
Root  crowning,  see  Crown 
Roots,  diseased,  133 
Rose's  fusible  metal,  124 


Salivary  calculus,  removal  of,  134 
Scalloped  clasp,  397 


662 


INDEX. 


Seabury's  vulcanizer,  542 
Seamless   contour  crowns,  selection  and 
adjustment  of,  280 

strengthening,  284 

repairing,  285 

supporting,  286 

altering  to  any  exact  form,  287 
Selecting  and  preparing  celluloid  blanks, 

579 
Separation  of  foreign  metals  from  gold, 

83 

of  teeth  for  clasps,  394 
Sheet-iron  furnace,  52 
Silex,  473 
Silver,  general  properties  of,  107 

alloys  of,  107 

refining  alloys  of,  108 

reduction  of,  to  required  forms,  1 10 

solders,  formulas  for,  1 1 1 
Similor,  122 

Snowden  and  Cowman's  vulcanizer,  537 
Solder,  gold,  91 

silver,  1 1 1 

brass,  122 

soft,  124 
Solid  fuels,  23 
Speculum  metal,  122 
Spiral  springs,  105 
Standard  clasp,  396 

gauge  plate,  102 
Starr's  method  of  bridge-work,  355 
Steam,  elastic  force  of,  at  different  tem- 
peratures, 553 
Steam  gauge,  Lawrence's,  554 

Coolidge's,  557 
Stowell's  method  of  setting  Logan  crown, 

220 
Substitution  of  plate  for  rubber  teeth,  563 
Suersen's  obturator,  648 
Supports,  50 

Surgical  treatment  of  the  mouth  after  ex- 
traction of  teeth,  135 
Swaged  gold  crown  caps,  272 


Table  of  fusible  alloys,  185 

temperaments,  439 
Tartar,  removal  of,  134 
Teeth  suital)le  for  clasping,  392 
Temporary  plates,  arranging  for,  461 
The  teeth  as  indicated  by  temperament, 

440 
Thickness  of  plate  for  clasps,  103 
Time  necessary  to  elapse  before  insert- 
ing artificial  teeth,  136 


Tin,  125 

Transparent  varnish,  formula  for,  165 

Treatment  of  the  mouth  preparatory  to 

the  insertion  of  artificial  teeth,  132 
Type  metal,  124 


Uniting  plate  and  clasp,  405 
Useless  and  diseased  remains  of  teeth, 
^33 


Varnish,  formulas  for,  165 

holder,  165 
Vulcanized  base-plate,  508 

methods   of  constructing  entire  den- 
tures in,  510 

Land's  teeth  for,  5 1 2 

flasking,  515 

packing  the  mold,  520 

vulcanizing,  526 

removing  flask  after,  558 

clasps  attached  to,  562 

plate  teeth  attached  to,  563 

repairing,  563 

finishing,  559 

partial  dentures  in,  561 

faced  with  celluloid,  601 
Vulcanizers,  535 

Hayes',  535 

Whitney's,  537 

Snowden  and  Cowman's,  537 

Mann's,  538 

Hood  and  Reynolds',  541 

Seabury's,  542 

Evans',  547 

Boston,  542 
Vulcanizing,  526 


Wax,  yellow,  141 

white,  142 
Weirich's  enamel  cleaver,  224 
White  Dental  Manufacturing  Company's 

system  of  bridge- work,  369 
Whitney's  vulcanizer,  537 
Williams'  method  of  bridge- work,  315 
Wire,  gold,  104 
Wood,  23 


Zinc,  123 
Zylonite,  605 


CATALOGUE 
No.  1. 


NOVEMBER,   1894. 

CATALOGUE 


Medical,  Dental, 

Pharmaceutical,  and   Scientific    Publications, 

WITH  A   SUBJECT  INDEX, 

PUBLISHED   BY 

P.  Blakiston,  Son  &  Co. 

(Successors  to  Lindsay  &  Blakiston), 

publishers,    IMPORTERS,    AND    BOOKSELLERS, 

IOI3  WALNUT  ST.,  PHILADELPHIA. 


THE  FOLLOWING  CATALOGUES  AND  CIRCULARS  'WILL  BE  SENT  FREE  TO 
ANY  ADDRESS  UPON  APPLICATION. 

This  Catalogue,  No.  i,  including  all  of  our  own  publicauons. 

A  Catalogue  of  Books  for  Dental  Students  and  Practitioners. 

Catalogues  of  Books  on  Chemistry,  Nursing,  Hygiene,  etc. 

A  Complete  Classified  Catalogue  of  all  Books  on  Medicine,  Dentistry,  Phar- 
macy, and  Collateral  Branches.     English  and  American. 

Sample  pages  of  Gould's  Dictionaries,  Morris's  Anatomy,  Moullin's 
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New  Illustrated  Catalogue  of  The  ?  Quiz-Compend  ?  Series. 


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GOULD'S   MEDICAL  DICTIONARIES.     Page  4. 

Physicians'  Visiting  Lists  and  Diaries.    See  page  32. 


CLASSIFIED  LIST,  WITH  PRICES, 

OF  ALL  BODKS  PUBLISHED  BY 

P.  BLAKISTON,   SON  &  CO.,   PHILADELPHIA, 

When  the  price  is  not  given  below,  the  book  is  out  of  print  or  about  to  be  published. 
Cloth  binding,  unless  otherwise  specified.     For  full  descriptions,  see  following  Catalogue. 


ANATOMY.  ' 
Ballou.     Veterinary  Anat.      ;Ji.oo 
Heath.    Practical.     7th  Ed.      5.00 
Holden.  Dissector.  Oil-cloth,  3.00 

Osteology.    -        -  6.00 

Landmarks.     4th  Ed.    1.25 

Macalister's  Text-Book. 

816  Illiis.  Clo.  7.50;  Sh.  8.50 

Morris.  Text  Book  of.  791  lUus. 

Clo.,  7.50;  Sh.,8.50;  J4Rus.,  9.50 
Potter.       Compend  of.       5th 

Ed.     133  Illustrations.  -  i.oo 

Wilson's  Anatomy,  nth  Ed.  6.00 

ANESTHETICS. 
Buxton.     Anaesthetics.   -  1.50 

Turnbull.     3d  Ed.  -         3.00 

ATLASES   AND  DIAGRAMS. 
Flower.     Of  Nerves.      -  3.50 

Marshall's    Phys.  and  Anat. 

Diagrams.  J40.00  and    60.00 

Schultze.  Obstet.  Diagrams.  26.00 

BRAIN  AND  INSANITY. 
Blackburn.     Autopsies.     -       1.25 
Gowers.       Diagnosis   of  Dis- 
eases of  the  Brain.     2d  Ed.      2.00 
Lewis    (Bevan).     Mental 

Diseases.         -        .        -  6.00 

Mann's  Psychological  Med.     5.00 
Stearns.    Mental  Dis     lUus.    3.00 
Tuke.     Dictionary  of  Psycho- 
logical Medicine.     2  Vols.     13.00 
V^ood.     Brain  and  Overwork.     .50 

CHEMISTRY. 
See  Technological  Books,  Water. 
Allen.     Commercial     Organic 
Analysis.  2d  Ed.  Volume  I.  

Volume  II.  -         -         

Volume  III.     Part  I.    

Volume  III.     Part  II.  5.00 

Volume  III.  Part  III. 

Bartley.     Medical  and  Phar- 
maceutical.    3d  Ed.         -        3.00 

Bloxam's  Text-Book.  7th  Ed.  4.50 
Bowman's  Practical.      -         2.00 
Caldwell.       Qualitative    and 
Quantitative  Analysis.    Net,  1.50 

Clowes.     Qual.  Analysis.         

Groves  and  Thorp.     Chemi- 
cal Technology.  Vol.  1.  Fuels  7.50 
Holland's  Urine,  Gastric  Con- 
tents, Poisons  and  Milk  Anal- 
ysis. 5th  Ed.     -        -        .         1.25 
Leffmann's  New  Compend.      i.oo 

Progressive  Exercises,  i.oo 

Milk  Analysi.s.     -       -  1.25 

Miitter.     Pract.  and  Anal.  1.25 

Ramsay.      Inorganic.    Illus.  4.50 

Richter's  Inorganic.    4th  Ed.  2.00 

Organic.     2d  Ed.  4.50 

Smith.      Electro-Chem.  Anal.  1.25 
Smith   and   Keller.     Experi- 
ments.    2d  Ed.     Illus.     Net,    .60 

Stammer.  Chem.  Problems.  .75 
Sutton.  Volumetric  Anal.  5.00 
Symonds.      Manual  of.  2.00 

Trimble,     Analytical.      -  1.50 

Watts.     (Fowne's)  Inorg.         2.25 

(Fowne's)  Organ.  2.25 

Wolff.     Applied  Medical.  i.oo 

■Woody.   Essentials  of.  3d  Ed.  1.25 

CHILDREN. 
Goodhart  and  Starr.  3.00;  Sh.3.50 

Hale.     Care  of.                 -  .75 

Hatfield.     Compend  of.  i.oo 

Meigs.      Infant   Feeding  and 

Milk  Analysis.                  -  i.oo 

Money.     Treatment  of.    -  3.00 

Muskett.     Treatment  of.  1,75 


Starr,    Digestive  Organs  of.    $2.25 

Hygiene  of  the  Nursery. i.oo 

CLINICAL  CHARTS. 
Davis.     Obstetrical.     Pads,        .50 
Griffiths.     Graphic.         "  .50 

Temperature  Charts,    "  .50 

COM  P  ENDS 
And  The  Quiz-Cotnpends. 
Ballou.     Veterinary  Anat.        i.oo 
Brubaker's  Physiol.  7th  Ed.    i.oo 
Fox  and  Gould,     The  Eye.  i.oo 
Hall.     Pathology.     Illus,  i.oo 

Hatfield.     Children.  -        i.oo 

Horwitz.  Surgery.  5th  Ed.  i.oo 
Hughes.  Practice.  2  Pts.  Ea.  i.oo 
Landis.  Obstetrics.  5th  Ed.  i.oo 
Leffmann's  Chemistry.  3d  Ed.  i.oo 
Mason.     Electricity.        -  i.oo 

Potter's    Anatomy,   5th  Ed.     i.oo 

Materia  Medica.  5th  Ed.  i.oo 

Stewart,  Pharmacy.  4th  Ed.  i.oo 
Warren.  Dentistry.  2d  Ed.  i.oo 
^Vells.     Gynaecology.      -         i.oo 

DEFORMITIES. 
Reeves.      Bodily   Deformities 


2.25 

1.25 
1-75 
4.00 


and  their  Treatment.     Illus 
DENTISTRY. 
Barrett.     Dental  Surg.   - 
Blodgett.  Dental  Pathology 
Flage.     Plastic  Filling.  - 
FilleBrown.   Op.  Dent.  Illus.  2.50 
Gorgas.     Dental  Medicine.       3.50 
Harris.     Principles  and  Prac.  7.00 

Dictionary  of.     5th  Ed.  5.00 

Heath.     Dis.  of  Jaws.      Net,  4.50 

Lectures  on  Jaws.  Bds.  i.oo 

Richardson.  Mech.  Dent.  4.50 
Sewell.  Dental  Surg.  -  3.00 
Stocken.  Materia  Medica.  2.50 
Taft,    Operative  Dentistry.       4.25 

,  Index  of  Dental  Lit.       2.00 

Talbot.  Irregularity  of  Teeth.  3.00 
Tomes,     Dental  Surgery.  5.00 

Dental  Anatomy.  4.00 

Warren's  (Compend  of.     -        i.oo 

Dental    Prostheses   and 

Metallurgy.     Illus.         -  1.50 

■White,    Mouth  and  Teeth.         .50 

DICTIONARIES. 
Cleveland's  Pocket  Medical.     .75 
Gould's  Illustrated  Dictionary 
of  Medicine,  Biology,  and  Al- 
lied Sciences,  etc.     Leather, 
Net,   gio.oo;     Half    Russia, 
Thumb  Index,        -        Net,  12  00 
Gould's  Medical  Student's  Dic- 
tionary. Yi  Lea.,  3.25;  }^  Mor. 
Thumb  Index.     -        -        .     4.25 
Gould's    Pocket     Dictionary. 
12,000  medical  words.    Lea., 
100:  Thumb  Inde.x,        -         1.25 
Harris'  Dental.  Clo.  5.00;  Shp.  6.00 
Longley's  Pronouncing.  i.oo 

Maxwell.  Terminologia  Med- 
ica Polyglotta.  -        -        4.00 
Treves.     German-English.        3.75 

DIRECTORY. 
Medical,  of  Philadelphia,    2.50 

EAR. 
Burnett.     Hearing,  etc.  .50 

Dalby.  Diseases  of.  4th  Ed.  3.50 
Hovell.     Treatise  on.        Net, soo 


Pritchard.     Diseases  of. 
ELECTRICITY. 

Bigelow.  Plain  Talks  on  Medi- 
cal Electricity.     43  Illus. 

Mason's    Electricity  and    its 
Medical  and  Surgical  Uses. 

Steavenson  &  Jones.  Medi- 
cal Electricity.     Illus,     - 


1.50 


EYE. 
Arlt,     Diseases  of.   -        -        J1.25 
Fox  and  Gould.    Compend.  i.oo 
Gower's  Ophthalmoscopy.        5.50 
Harlan.     Eyesight.  -  .50 

Hartridge.  Refraction.  sthEd.  1.75 

Ophthalmoscope,    -         1.50 

Hansen   and    Bell.     Clinical 

Ophthalmology.      120  Illus.      1.75 
Higgins.     Practical  Manual.    1.75 
Macnamara.     Diseases  of.       4.00 
Meyer  and    Fergus.      Com- 
plete Text-Book,  with  Colored 
Plates.  270  Illus.  Clo.  4.50:  Sh.5.so 
Morton.     Refraction.  4th  Ed.  i.oo 
Phillips,   Spectacles  and  Eye- 
glasses.    47  Illus.  -  I.oo 
Swanzy's  Handbook.  4th  Ed.  3.00 

FEVERS. 
Collie,  On  Fevers.    -  2.50 

HEADACHES. 
Day,     Their  Treatment,  etc.     1.25 
HEALTH  AND  DOMESTIC 
MEDICINE. 
Bulkley,    The  Skin.         -  .50 

Burnett.     Hearing.  -  .50 

Cohen.     Throat  and  Voice.         .50 
Dulles,   Emergencies.  4th  Ed.  1.00 


.50 
•5° 
.50 
•50 
■5° 
.50 
75 


Harlan.     Eyesight 
Hartshorne.    Our  Homes, 
Lincoln,     School  Hygiene. 
Osgood,     Dangers  of  Winter. 
Packard.    Sea  Air,  etc. 
Richardson's  Long  Life. 
Tanner.   On  Poisons.    7th  Ed. 
Westland.     The  Wife  and 

Mother.         ...  2.00 

White,  Mouth  and  Teeth.  .50 
Wilson,  Summer  and  its  Dis.  .50 
Wood.     Overwork.  -  .50 

HEART. 

Sansom.     Diseases  of.       -        7.50 

HYGIENE. 

See  Water. 

Canfield.   Hygiene  of  the  Sick- 

Room,      -        .        -        -        1.50 
Coplin  and  Bevan,     Practi- 
cal Hygiene.     Illus.        -        4.00 
Fox,     Water,  Air,  Food.  4.00 

Kenwood,       Public     Health 

Laboratory  Guide.  -  3.00 

Lincoln.  School  Hygiene.  .50 
Parke's  (E.)  Hygiene.  8th  Ed.  5.00 

(L.  C.),  Manual.  2.75 

Starr.  Hygieneof  the  Nursery,  i.oo 

Stevenson  and  Murphy.  A 

Treatise  on  Hygiene.     In  2 

Vols.  Vol.  1,     7.50 

Vol.  II,     7.50 

W^ilson's  Handbook.   7th  Ed.  3.25 

Weyl.     Coal-Tar  Colors,  1.25 

JOURNALS,  Etc. 
Archives  of  Surgery.  4  Nos.  3.00 
Ophthalmic  Review.  12     "     3.00 
New  Sydenham  Society's 

Publications     ...        8.00 
KIDNEY  DISEASES, 
Ralfe.     Dis.  of  Kidney,  etc.     2.75 
Thornton.     Surg,  of  Kidney.  1.75 
Tyson.     Bright's   Disease 
and  Diabetes,  Illus. 

MASSAGE. 
Kleen  and  Hartwell, 
Murrell,     Massage,  sth  Ed. 
Ostrom,   Massage.  87  Illus. 

MATERIA  MEDICA. 
Biddle,     13th  Ed.  Cloth,  4.25 

Davis.     Essentials  of  Materia 
Med.  and  Pres.  Writing.  Net,  1,5 


3-5° 

2.75 
1,50 
I.oo 


CLASSIFIED  LIST  OF  P.  BLAKISTON,  SON  (&-  CO:S  PUBLICATIONS. 


Gorgas.  Dental.  4th  Ed.  $3.50 
Potter's  Compend  of.  5th  Ed.  i.oo 
Potter's  Handbook  of.  Fourth 

Ed.    Cloth,  4.00;  Sheep,  5.00 

Sayre.   Organic  Materia  Med. 

and  Pharmacognosy.        -  4.50 

^A^hite  &  Wilcox.  Mat.  Med., 

Pharmacy,       Pharmacology, 

and    Therapeutics.     2d  Ed. 

Enlarged.    Cloth,  3.00;  Sh.    3.50 

MEDICAL  JURISPRUDENCE. 
Mann.  Forensic  Med.  Net,  6.50 
Reese.  Medical  Jurisprudence 

&Toxicology,  3d  Ed. 3.00;  Sh.  3.50 

MICROSCOPE. 

Beale.     How  to  Work  with.     7.50 

In  Medicine.         -  7.50 

Carpenter.     The  Microscope. 

7th  Ed.  800  Illus.Cl.  6.50;  Lea. 7.50 
Lee.  Vade  Mecum  of.  Net,  4.00 
MacDonald.     Examination  of 

Water  by.        -        -        -  2.75 

Reeves.  Medical  Microscopy. 

lUustrated.  -  -  Net,  2.50 
Wethered.     Medical  Micros-  j 

copy.     lUus.        -        -        .     2.50  { 
MISCELLANEOUS.  j 

Black.     Micro-organisms.  .75  j 

Burnet.     Food  and  Dietaries.  1.75  \ 
Davis.    Text-book  of  Biology.  4.00  I 
Duckworth.     On  Gout.        -     7.00  | 
Garrod.     Rheumatism,  etc.      6.00  ] 
Haddon.     Embryology.       -    6.00 
Haig.     Uric  Acid.         -        -    3.50  ! 
Hare.     Mediastinal  Disease.     2.00 
Henry.     Anaemia.         -        -      -75 
Hilton.     Rest  and  Pain.       -     3.00 
Powell.     Lungs,  etc.    -        -    5.00 
Treves.     Physical  Education.  1.25 

NERVOUS  DISEASES,  Etc. 
Flower.    Atlas  of  Nerves.         3.50 
Bowlby.     Injuries  of.        -        4.50 
Govt^ers.    Manual  of.     2d  Ed. 

530  lUus.  Vol.  1,3.50  ;  Vol.  2,  4.50 
Syphilis  and  the  Nerv- 
ous System.        ...      i.oo 

Diseases  of  Brain.  2.00 

Horsley.      Brain   and    Spinal 

Cord.  lUus.  -  -  .  3.00 
Obersteiner.  Central  Nervous 

System.  ....  6.00 
Ormerod.  Manual  of.  -  2.00 
Osier.     Cerebral  Palsies.  2.00 

Chorea  -  -         2.00 

Page.     Injuries  of  Spine.  

Railway  Injuries.       -      2.25 

Thorburn.      Surgery    of    the 

Spinal  Cord.  ...  4.50 
Watson.    Concussions.  i.oo 

NURSING. 
Canfield.  Hygiene  of  the  Sick- 

Room.  ....  1.50 
CuUingworth.    Manual  of.        .75 

Monthlj'   Nursing.  .50 

Domville's  Manual.  7th  Ed.  .75 
FuUerton.     Obst.  Nursing.      1.25 

Nursing    in    Abdominal 

Surg,  and  Dis.  of  Women,  1.50 

Humphrey.  Manual.  lothEd.  1.25 
Shawe.  District  Nursing.  1.00 
Starr.  Hygiene  of  the  Nursery,  i.oo 
Temperature  Charts.    -  .50 

Voswinkel.    Surg.  Nursing.    

OBSTETRICS. 
Bar.     Antiseptic  Midwifery,      i.oo 
Cazeauxand  Tarnier.   Text- 
Book  of.     Colored  Plates.        5.00 
Davis.     Obstetrical  Chart.  .50 

Davis.  Obstetrics.  Illus.  2.50 
Landis.  Compend.  jih  Ed.  i.oo 
Schultze.  Obstetric  Diagrams. 

20  Plates,  map  size.  Net^  26.00 
Strahan.  Extra-Uterine  Preg.  .75 
Winckel's  Text-book.  6.00 

PATHOLOGY  &  HISTOLOGY. 
Blackburn.     Autopsies.  1.25 

Blodgett.  Dental  Pathology  1.75 
Gilliam.     Essentials  of.     -  .75 

Hall's  Compend.     Illus.       -     i.oo 


Stirling's  Practical  Histology. 

zdlEd.     368  Illustrations.      $3.00 
Sutton.     Pathology  -  4.50 

Virchow.     Post-mortems.  i.oo 

PHARMACY 
Beasley's  Receipt-Book.      -     2.25 

Formulary.      -        -  2.25 

Coblentz.  Manual  of  Pharm.  4.00 
Proctor.  Practical  Pharm.  4.50 
Robinson.  Latin  Grammar  of.  2.00 
Sayre.    Organic  Materia  Med. 

and  Pharmacognosy.       -  4.50 

Stewart's  Compend.  4th  Ed.  i.oo 
U.   S.   Pharmacopoeia.     7th 

Revision.  AV/,Cl.2.5o;  Sh.,  3.00 

Select  Tables  from  U.S.  P.       .25 

White  and  Wilcox.  Materia 

Medica  and  Phar.     2d  Ed.      3.00 

PHYSICAL  DIAGNOSIS. 

Tyson's  Manual.  2d  Ed.  Illus.  1.50 

PHYSIOLOGY. 
Brubaker's  Compend.     Illus- 
trated.    7th  Ed.      -        -  I.oo 
Kirkes'  New  13th  Ed.     (Au- 
thor's Ed.)  Cloth,  4.00;   Sh.,s.oo 
Landois'  Text-book.  845  Illus- 
trations. 4th  Ed.  C1.7  0o;Sh.  8.00 
Sanderson's  Laboratory  B'k.  5.00 
Starling.     Elements  of.       -      2.00 
Stirling.     Practical  Phys.         3.00 
Tyson's  Cell  Doctrine.       -       2.00 
Veo's  Manual.  254  Illustrations 
6th  Ed.    Cloth,  3.00;  Sheep,  3.50 
POISONS. 
Murrell.     Poisoning.         -        1.25 
Reese.     Toxicology.     3d  Ed.   3.00 
Tanner.     Memoranda  of.  .75 

PRACTICE. 
Beale.    Slight  Ailments.  1.25 

Charteris,  Guide  to.        -  3.00 

Fagge's  Practice.  2  Vols.  8.00 
Fowler's  Dictionary  of.  -  5.00 
Hughes.  Compend  of.  2  Pts.  2.00 

Physicians'  Edition. 

I  Vol.  Morocco,  Gilt  edge.  2.50 
Roberts.  Text-book,  iith  Ed.  5.50 
Taylor's  Manual  of.     -  2.00 

PRESCRIPTION  BOOKS. 
Beasley's  3000  Prescriptions.   2.25 

Receipt  Book.        -  2.25 

Formulary.     -         -  2.25 

Davis.     Materia   Medica  and 

Prescription  Writing.  Net,  1.50 
Pereira's  Pocket-book.  i.oo 

Wythe's  Dose  and  Symptom 
Book.     17th  Ed.     -.        -         I.oo 
SKIN." 
I    Anderson's  Text- Book.  4.50 

I    Bulkley.    The  Skin.         -  .50 

1    Crocker.    Dis.  of  Skin.    Illus.  5.00 
I    Van   Harlingen.     Diagnosis 
j        and  Treatment  of  Skin  Dis. 

3d  Fd.     Illus.  -         .         

I    STIMULANTS  &  NARCOTICS. 

I    Lizars.     On  Tobacco.      -  .50 

Parrish.     Inebriety.         -  1.25 

SURGERY  AND  SURGICAL 

DISEASES. 
Caird  and  Cathcart.    Surg- 
geon's  Pocket-Book. 

Leather,  Net,  2.50 
Dulles.  Emergencies.  -  i.oo 
Hacker.  Wounds.  -  -  .75 
Heath's  Minor.  loth  Ed.  2.00 
Diseases  of  Jaws.   Net,  4.50 

Lectures  on  Jaws.  i.oo 

Horwitz.  Compend.   5th  Ed.   i.oo 
Jacobson.     Operations  of.    -     5.00 
Macready  on  Ruptures    Net,  6.00 
Moullin.      Complete     Text- 
book     2d   Fd.  by  Hamilton, 
600  Illustrations  and  Colored 
Plates.     Net,  CI.  7.00;  Sh.   8.00 
Yi  Rus.  ...         9.00 

Porter's    Surgeon's    Pocket. 

book.  -        -    Leather    2.25 

Smith.  Abdominal  Surg.  7.00 
■Walsham.  Practical  Surg.  3.00 
Watson's  Amputations.  5.50 


4.00 
5.00 
I-7S 
1-75 

1. 25 

50 


TECHNOLOGICAL  BOOKS. 

See  also  Chemistry . 
Cameron.  Oils  &  Varnishes.  $2.50 

Soap  and  Candles.         2.25 

Gardner.     Brewing,  etc.  ^•7S 

Gardner.    Bleaching   and 

Dyeing.    -        -        .        .         1.75 
Groves  and  Thorp.    Chemi- 
cal   Technology.       Vol.     I. 
Millson  Fuels.  CI.  7.50;  J^M.  9.00 
Overman.     Mineralogy.     -       i.oo 

THERAPEUTICS. 
Allen,  Harlan,  Harte,  Van 
Harlingen.     Local  Thera. 
Biddle.  13th  Ed.  CI.  4.25;  Sh. 
Burnet.    Food  and  Dietaries. 
Field,  Cathartics  and  Emetics. 
Mays.     Therap.  Forces. 
— —  Theine         ... 
Napheys'  Therapeutics.  Vol. 
I.     Medical  and   Disease  of 
Children.       -       Cloth,  A''<?^,  4.00 

Vol.  2.  Surgery.  Gynsec. 

&  Obstet.  -  Cloth,  Net,  4.00 
Potter's  Compend.     5th  Ed.     i.oo 

,  Handbook  of.  4.00  ;  Sh.  5.00 

White   and    Wilcox.     Mat. 
Med.  Pharmacy,  Pharmacol- 
ogy, and   Thera.     2d  Ed.        3.00 
■Waring's  Practical.    4th  Ed.  3.00 

THROAT  AND  NOSE. 
Cohen.     Throat  and  Voice.        .50 
Hall.     Nose  and  Throat.     -      3.00 
Hutchinson.  Nose  &  Throat.  1.25 
Mackenzie.     Throat  Hospital 

Pharmacopoeia.  5th  Ed.  1.25 
McBride.      Clinical  Manual, 

Colored  Plates,  -  -  7.00 
Murrell.  Bronchitis.  .  1.50 
Potter.  Stammering,  etc.  i.oo 
Woakes.  Post-Nasal  Catarrh.  1.50 

TRANSACTIONS  AND 

REPORTS. 

Trans.  College  of  Physicians.  3.50 

Assoc.  Amer.  Phys.   3.50 

URINE  &  URINARY  ORGANS. 
Acton.     Repro.  Organs.  2.00 

Beale.  Urin.  Deposits.  Plates.  2.00 
Holland.  The  Urine,  Milk  and 

Common  Poisons.  5th  Ed.  i.oo 
Legg.  On  Urine.  7th  Ed.  'i.oo 
Marshall  and  Smith.  Urine,  i.oo 
Memminger.     Diagnosis   by 

the  Urine.     IlUis.     -         -  i.oo 

Ralfe.  Kidney  and  Uri.  Org.  2.75 
Thompson.  Urinary  Organs.   3.50 

Calculous  Dis.  3d.  Ed.    i.oo 

Thornton.  Surg,  of  Kidney.  1.75 
Tyson.  Exam,  of  Urine.  1.50 
Van  Niiys.    Urine  Analysis,     i.oo 

VENEREAL  DISEASES. 
Hill  and  Cooper's  Manual,    i.oo 
Gowers.      Syphilis   and    the 

Nervous  System.  -  -  i.oo 
Jacobson.     Diseases  of  Male 

Organs.     Illustrated.       Net,  6.00 

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Armatage.     Vet.  Rememb.  1.25 

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General  Contents — Diet  in  Derangements  of  the  Digestive,  Nervous,  and  Res- 
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BYFORD.  Diseases  of  Women.  The  Practice  of  Medicine  and  Surj^^ery,  as 
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A.M.,  M.D.,  Professor  of  Gynsecology  in  Rush  Medical  College,  etc.,  and  Henry 
T.  Byford,  m.d..  Surgeon  to  the  Woman's  Hospital  of  Chicago;  Gynaecologist 
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C  ^IRD  AND  CATHCART.  Surgical  Handbook.  For  the  Use  of  Students  and 
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COLLIE,  On  Fevers.  A  Practical  Treatise  on  Fevers,  Their  History,  Etiology, 
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m.d.,  Ass't  Department  of  Hygiene,  Jefferson  Medical  College;  Bacteriologist, 
St.  Agnes'  Hospital,  Philadelphia,  with  an  Introduction  by  Prof.  H.  A.  Hare, 
and  articles  on  Plumbing,  Ventilation,  etc.,  by  Mr.  W.  P.  Lockington,  Editor  of 
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CROCKER.  Diseases  of  the  Skin.  Their  Description,  Pathology,  Diagnosis,  and 
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Radcliffe  Crocker,  m.d..  Physician  to  the  Dept.  of  Skin  Diseases,  University 
College  Hospital,  London.  92  Illustrations.  Second  Edition.  Enlarged.  987 
pages.     Octavo.  Cloth,  $5.00 

CITLLINGWORTH.   A  Manual  of  Nursing,  Medical  and  Surgical.    By  Charles 

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DALBY.  Diseases  and  Injuries  of  the  Ear.  By  Sir  William  B.  Dalby,  m.d.. 
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DAVIS.  A  Manual  of  Obstetrics.  Being  a  complete  manual  for  Physicians  and 
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Infancy  in  the  Philadelphia  Polyclinic,  Clinical  Lecturer  on  Obstetrics,  Jeffer- 
son Medical  College ;  Professor  of  Diseases  of  Children  in  Woman's  Medical 
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DOMVILLE.  Manual  for  Nurses  and  others  engaged  in  attending  to  the  sick.  By 
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DUCKWORTH.  On  Gout.  Illustrated.  A  treatise  on  Gout.  By  Sir  Dyce 
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FILLEBROWN.  A  Text-Book  of  Operative  Dentistry.  Written  by  invitation 
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versity;  Member  of  the  American  Dental  Assoc,  etc.    Illus.    8vo.      Clo.,  $2.50 

FLAGG.  Plastics  and  Plastic  Fillings,  as  pertaining  to  the  filling  of  all  Cavities 
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cavities  in  teeth  of  all  grades  of  structure.  By  J.  Foster  Flagg,  d.d.s.,  Professor 
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of  the  Cutaneous  Surface  and  to  all  the  Muscles.  By  William  H.  Flower, 
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FOWLER'S  Dictionary  of  Practical  Medicine.  By  Various  Writers.  An  Ency- 
clopedia of  Medicine.  Edited  by  James  Kingston  Fowler,  m.a.,  m.d.,  f.r.c.p., 
Senior  Asst.  Physician  to,  and  Lecturer  on  Pathological  Anatomy  at,  the  Mid- 
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FOX   AND   GOULD.     Compend  on  Diseases  of  the  Eye  and  Refraction, 

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Assistant,  Ophthalmological  Department,  Jefferson  Medical  College  Hospital ; 
Ophthalmic  Surgeon,  Germantown  Hospital,  Philadelphia ;  late  Clinical  Assistant 
at  Moorfields,  London,  England,  etc.,  and  Geo.  M.  Gould,  m.d.  Second  Edition. 
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Series.  Cloth,  $1.00.      Interleaved  for  the  addition  of  notes,  $1.25 

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Mothers.     By  Anna  M.  Fullerton,  m.d..  Demonstrator  of  Obstetrics  in  the 

Woman's   Medical   College ;     Physician   in   charge   of,    and   Obstetrician    and 

Gynaecologist  to,  the  Woman's   Hospital,   Philadelphia,  etc.     38   Illustrations. 

Third  Edition.     Revised  and  Enlarged.     i2mo.  Cloth,  $1.25 

Nursing  in  Abdominal  Surgery  and  Diseases  of  Women.    Comprising  the 

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GARROD.  On  Rheumatism.  A  Treatise  on  Rheumatism  and  Rheumatic  Arthritis. 
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GARDNER.    The  Brewer,  Distiller  and  Wine  Manufacturer.    A  Handbook  for 

all  Interested  in  the  Manufacture  and  Trade  of  Alcohol  and  Its  Compounds. 

Edited  by  John  Gardner,  f.c.s.     Illustrated.  Cloth,  $1.75 

Bleaching^,  Dyeing,  and  Calico  Printing.  With  Formulae.    Illustrated.     $1.75 

GILLIAM'S  Pathology.  The  Essentials  of  Pathology;  a  Handbook  for  Students. 
By  D.  Tod  Gicliam,  m.d..  Professor  of  Physiology,  Starling  Medical  College, 
Columbus,  O.    With  47  Illustrations.    i2mo.  Cloth,  .75 

GOODHART  and  STARiR'S  Diseases  of  Children.  The  Student's  Guide  to  the 
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Hospital  for  Children  and  to  Guy's  Hospital.  Second  American  from  the  Third 
English  Edition.  Rearranged  and  Edited,  with  notes  and  additions,  by  Louis 
Starr,  m.d..  Clinical  Professor  of  Diseases  of  Children  in  the  University  of 
Pennsylvania;  Physician  to  the  Children's  Hospital.  With  many  new  prescrip- 
tions. Cloth,  §3.00;  Leather,  ^3.50 

GORGAS'S  Dental  Medicine.  A  Manual  of  Materia  Medica  and  Therapeutics. 
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Science,  Dental  Surgery  and  Dental  Mechanism  in  the  Dental  Dep.  of  the  Univ. 
of  Maryland.     Fifth  Edition.     Revised  and  Enlarged.     8vo.  In  Press. 

GOULD.    The  Illustrated  Dictionary  of  Medicine,  Biology,  and  Allied  Sciences. 

Being  an  Exhaustive  Lexicon  of  Medicine  and  those  Sciences  Collateral  to  it : 
Biology  (Zoology  and  Botany),  Chemistry,  Dentistry,  Pharmacology,  Microscopy, 
etc.  By  George  M.  Gould,  m.d.,  Editor  of  The  Medical  Neius ;  President 
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based  on  Recent  Medical  Literature.    With  Tables  of  the  Bacilli,  Micrococci, 

Leucomaines,  Ptomaines,  etc.,  of  the  Arteries,  Muscles,  Nerves,  Ganglia  and 

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12  P.  BLAKISTON,  SON  &-  CO.'S 

GOWERS,  Manual  of  Diseases  of  the  Nervous  System.  A  Complete  Text-book. 
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London.  Physician  to  National  Hospital  for  the  Paralyzed  and  Epileptic.  Second 
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Illustrations.     Two  Volumes.     Octavo. 

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Vol.  II.     Diseases  of   the    Brain    and    Cranial    Nerves;    General  and 
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Syphilis  and  the  Nervous  System.  Being  a  revised  reprint  of  the  Lettso- 
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Diagnosis  of  Diseases  of  the  Brain.  8vo.  Second  Ed.  lUus.  Cloth,  #2.00 
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changes  of  the  Eye  in  Diseases  of  the  Brain,  Kidney,  etc.  Third  Edition. 
Revised,  with  the  assistance  of  R.  Marcus  Gunn,  f.r.c.s.,  Surgeon,  Royal 
London  Ophthalmic  Hospital,  Moorfields.     Octavo.  Cloth,  ^5.50 

GROVES  AND  THORP.  Chemical  Technology.  A  new  and  Complete  Work. 
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umes, with  numerous  illustrations.     £ac/i  volume  sold  separately. 

Vol.  I.  Fuel.  By  Dr.  E.  J.  Mills,  f.r.s..  Professor  of  Chemistry,  Anderson 
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HACKER.  Antiseptic  Treatment  of  "Wounds,  Introduction  to  the,  according  to 
the  Method  in  Use  at  Professor  Billroth's  Clinic,  Vienna.  By  Dr.  Victor  R.  v. 
Hacker,  Assistant  in  the  CHnic  Billroth,  Professor  of  Surgery,  etc.  Authorized 
Translation,  by  Surgeon-Captain  C.  R.  Kilkelly,  m.b.,  British  Army  Medical 
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HADDON'S  Embryology.  An  Introduction  to  the  Study  of  Embryology.  For 
the  Use  of  Students.  By  A.  C.  Haddon,  m.a.,  Prof,  of  Zoology,  Royal  College 
of  Science,  Dublin.     190  Illustrations.  Cloth,  $6.cx5 

HAIG.  Causation  of  Disease  by  Uric  Acid.  A  Contribution  to  the  Pathology  of 
High  Arterial  Tension,  Headache,  Epilepsy,  Gout,  Rheumatism,  Diabetes, 
Bright's  Disease,  etc.  By  Alex.  Haig,  m.a.,  m.d.  (Oxon).,  f.r.c.p..  Physician  to 
Metropolitan  Hospital,  London.     Illustrated.     New  Edition.  Cloth,  $3.50 

HALE.  On  the  Management  of  Children  in  Health  and  Disease.  A  Book  for 
Mothers.  By  Amie  M.  Hale,  m.d.  New  Enlarged  Edition.  i2mo.  Cloth,  .75 
HALL.  Compend  of  General  Pathology  and  Morbid  Anatomy.  ByH.NEWBERY 
Hall,  ph.g.,  m.d.,  Professor  of  Pathology  and  Medical  Chemistry ;  Post-Graduate 
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tions. No.  i§  fQuiz-Competid?  Series.  Cloth,  $1.00.  Interleaved  for  Notes,  $1.25 
HALL.  Diseases  of  the  Nose  and  Throat.  By  F.  De  Havilland  Hall,  m.d., 
f'.R.C.p.  (Lond.),  Physician  in  charge  Throat  Department  Westminster  Hospital; 
Joint  Lecturer  on  Principles  and  Practice  of  Medicine,  Westminster  Hospital 
Medical  School,  etc.  Two  Colored  Plates  and  59  other  Illustrations.  i2mo. 
524  pages.  Cloth,  $3.00 

HANSELL  and  BELL.  Clinical  Ophthalmology,  Illustrated.  A  Manual  for 
Students  and  Physicians.  By  Howard  F.  Hansell,  a.m.,  m.d.,  Lecturer  on 
Ophthalmology  in  the  Jefferson  College  Hospital,  Philadelphia,  etc.,  and  James 
H.  Bell,  m.d.,  late  Demonstrator  of  Anatomy  in  Jefferson  Medical  College; 
Member  Ophthalmic  Staff,  Jefferson  College  Hospital;  Ophthalmic  Surgeon, 
Southwestern  Hospital,  Phila.  With  Colored  Plate  of  Normal  Fundus  and  120 
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HARE.  Mediastinal  Disease.  The  Pathology,  Chnical  History  and  Diagnosis  of 
Affections  of  the  Mediastinum  other  than  those  of  the  Heart  and  Aorta.  By  H.  A. 
Hare,  m.d.  (Univ.  of  Pa.),  Professor  of  Materia  Medica  and  Therapeutics  in 
Jefferson  Medical  College,  Phila.     8vo.     Illustrated  by  Six  Plates.       Cloth,  $2.00 

HARLAN.  Eyesight,  and  How  to  Care  for  It.  By  George  C.  Harlan,  m.d., 
Prof,  of  Diseases  of  the  Eye,  Philadelphia  Polyclinic.     Illustrated.         Cloth,  .50 

HARRIS'S  Principles  and  Practice  of  Dentistry.  Including  Anatomy,  Physi- 
ology, Pathology,  Therapeutics,  Dental  Surger}^  and  Mechanism.  By  Chapin  A. 
Harris,  m.d.,  d.d.s.,  late  President  of  the  Baltimore  Dental  College,  author  of 
"Dictionary  of  Medical  Terminology  and  Dental  Surgery."  Twelfth  Edition, 
Revised  and  Edited  by  Ferdinand  J.  S.  Gorgas,  a.m.,  m.d.,  d.d.s.,  author  of 
"Dental  Medicine;"  Professor  of  the  Principles  of  Dental  Science,  Dental 
Surgery  and  Dental  Mechanism  in  the  University  of  Maryland.  Two  Full-page 
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Dictionary  of  Dentistry.  Fifth  Edition,  Revised.  Including  Definitions  of 
such  Words  and  Phrases  of  the  Collateral  Sciences  as  Pertain  to  the  Art  and 
Practice  of  Dentistry.  Fifth  Edition.  Rewritten,  Revised  and  Enlarged. 
By  Ferdinand  J.  S.  Gorgas,  m.d.,  d.d.s.,  Author  of  "Dental  Medicine;" 
Editor  of  Harris's  "Principles  and  Practice  of  Dentistry;"  Professor  of 
Principles  of  Dental  Science,  Dental  Surgery,  and  Prosthetic  Dentistry  in  the 
University  of  Maryland.     Octavo.  Cloth,  $5.00  ;  Leather,  $6.00 

HARTRIDGE.  Refraction.  The  Refraction  of  the  Eye.  A  Manual  for  Students. 
By  Gustavus  Hahtridge,  f.r.c.S.,  Consulting  Ophthalmic  Surgeon  to  St.  Bar- 
tholomew's Hospital ;  Ass't  Surgeon  to  the  Royal  Westminster  Ophthalmic  Hos- 
pital, etc.     96  Illustrations  and  Test  Types.     Seventh  Edition.  Cloth,  $1.75 

On  The  Ophthalmoscope,     A  Manual  for  Physicians  and  Students.     Second 

Edition.    With  Colored  Plates  and  many  Woodcuts.     i2mo.        Cloth,  $1.50 

HARTSHORNE.     Our  Homes.     Their  Situation,  Construction,  Drainage,  etc.     By 

Henry  Hartshorne,  m.d.     Illustrated.  Cloth,  .50 

HATFIELD.  Diseases  of  Children.  By  Marcus  P.  Hatfield,  Professor  of 
Diseases  of  Children,  Chicago  Medical  College.  With  a  Colored  Plate.  Being 
N0.14,?  Quiz-Co7>ipend  f  Series.     i2mo.  Cloth,  fi. 00 

Interleaved  for  the  addition  of  notes,  $1.25 

HEATH'S  Minor  Surgery  and  Bandaging,    By  Christopher  Heath,  f.r.c.s., 

Holme   Professor  of  Chnical   Surgery   in   University  College,  London.     Tenth 

Edition.      Revised  and   Enlarged.     With    158    Illustrations,  62  Formulae,  Diet 

List,  etc.     i2mo.  Cloth,  $2.00 

Practical  Anatomy.      A  Manual  of  Dissections.      Eighth  London  Edition. 

300  Illustrations.  Cloth,  $5.00 

Injuries  and  Diseases  of  the  Jaws.    Fourth  Edition.    Edited  by  Henry 

Percy   Dean,    m.s.,  f.r.c.s.,  Assistant   Surgeon    London  Hospital.     With 

187  Illustrations.    Svo.  Cloth,  Ne{,  $4.50 

Lectures  on  Certain  Diseases  of  the  Jaws,  delivered  at  the  Royal  College  of 
Surgeons  of  England,  1887.     64  Illustrations.     Svo.  Boards,  $1.00 

HENRY.  Anaemia.  A  Practical  Treatise.  By  Fred'k  P.  Henry,  m.d.,  Physician 
to  Episcopal  Hospital,  Philadelphia.  Half  Cloth,  .75 

HIGGENS' Ophthalmic  Practice,  By  Charles  Higgens,  f.r.c.s.  IUus.  Cloth,  $1.75 

HILTON.  Rest  and  Pain.  A  Course  of  Lectures  on  the  Influence  of  Mechanical 
and  Physiological  Rest  in  the  Treatment  of  Accidents  and  Surgical  Diseases 
and  the  Diagnostic  Value  of  Pain.  By  John  Hilton,  f.r.s.  Edited  by  W.  H. 
A.  Jacobson,  f.r.c.s.     Octavo.     504  pages.  Cloth,  $3.00 


14  P.  BLAKISTON,  SON  &-  CO:S 

HILL  AND  COOPER.  Venereal  Diseases.  The  Student's  Manual  of  Venereal 
Diseases,  being  a  concise  description  of  those  Affections  and  their  Treatment. 
By  Berkeley  Hill,  m.d.,  Professor  of  Clinical  Surgery,  University  College,  and 
Arthur  Cooper,  m.d.,  Late  House  Surgeon  to  the  Lock  Hospital,  London. 
4th  Edition.     i2mo.  Cloth,  $i.oo 

HOLDEN'S  Anatomy.  Sixth  Edition.  A  Manual  of  the  Dissections  of  the  Human 
Body.  By  John  LaNigton,  f.r.c.s.,  Surgeon  to,  and  Lecturer  on  Anatomy  at, 
St.  Bartholomew's  Hospital.  Carefully  Revised  by  A.  Hewson,  m.d.,  Demonstra- 
tor of  Anatomy,  Jefferson  Medical  College  ;  Chief  of  Surgical  Clinic,  Jefferson 
Hospital;  Mem.  Assoc.  Amer.  Anatomists,  etc.  311  Illustrations.  i2mo.  800 
pages.  Cloth,  $3.00;  Oil-cloth,  ;?;3.oo  ;  Leather,  $3.50 

Human  Osteology.  Comprising  a  Description  of  the  Bones,  with  Colored 
Delineations  of  the  Attachments  of  the  Muscles.  The  General  and  Micro- 
scopical Structure  of  Bone  and  its  Development.  Carefully  Revised,  by 
the  Author  and  Prof.  Stewart,  of  the  Royal  College  of  Surgeons'  Museum. 
With  Lithographic  Plates  and  Numerous  Illustrations.  7th  Ed.  Cloth,  $6.00 
Landmarks.     Medical  and  Surgical.     4th  Edition.     8vo.  Cloth,  $1.25 

HOLLAND.  The  Urine,  the  Gastric  Contents,  the  Common  Poisons  and  the 
Milk.  Memoranda,  Chemical  and  Microscopical,  for  Laboratory  Use.  By  J.  W. 
Holland,  m.d,.  Professor  of  Medical  Chemistry  and  Toxicology  in  Jefferson 
Medical  College,  of  Philadelphia.  Fifth  Edition,  Enlarged.  Illustrated  and 
Interleaved.  i2mo.  Cloth,  $1  25 

HORSLEY.  The  Brain  and  Spinal  Cord.  The  Structure  and  Functions  of.  Being 
the  Fullerian  Lectures  on  Physiology  for  1891.  By  Victor  A.  Horsley,  m.b., 
F.R.S.,  etc..  Assistant  Surgeon,  University  College  Hospital,  Professor  of  Pathology, 
University  College,  London,  etc.     With  numerous  Illustrations.  Cloth,  513.00 

HORWITZ'S  Compend  of  Surgery,  including  Minor  Surgery,  Amputations,  Frac- 
tures, Dislocations,  Surgical  Diseases,  and  the  Latest  Antiseptic  Rules,  etc.,  with 
Differential  Diagnosis  and  Treatment.  By  Orville  Horwitz,  b.s.,  m.d.,  Pro- 
fessor of  Genito-Urinary  Diseases,  late  Demonstrator  of  Surgery,  Jefferson  Medi- 
cal College.  Fifth  Edition.  Very  much  Enlarged  and  Rearranged.  Over  300 
pages.     167  Illustrations  and  98  Formulae.    i2mo.  No.  g  ?  Qiciz-Cotnpendf  Series. 

Cloth,  |;i.oo.     Interleaved  for  notes,  $1.25 

HUGHES.    Compend  of  the  Practice  of  Medicine.    Fifth  Edition.    Revised  and 

Enlarged.    By  Daniel  E.  Hughes,  m.d..  Demonstrator  of  Clinical  Medicine  at 

Jefferson  Medical  College,  Philadelphia.     In  two  parts.     Being  Nos.  2  and  j, 

?  Quiz-  Compend  f  Series. 

Part  I. — Continued,  Eruptive  and  Periodical  Fevers,  Diseases  of  the  Stomach, 
Intestines,  Peritoneum,  Biliary  Passages,  Liver,  Kidneys,  etc.,  and  General 
Diseases,  etc. 

Part  II. — Diseases  of  the  Respiratory  System,  Circulatory  System  and  Ner- 
vous System  ;  Diseases  of  the  Blood,  etc. 

Price  of  each  Part,  in  Cloth,  $1.00 ;  interleaved  for  the  addition  of  Notes,  $1.25 
Physicians'  Edition. — In  one  volume,  including  the  above  two  parts,  a  sec- 
tion on  Skin  Diseases,  and  an  index.      Fifth  revised,  enlarged  Edition. 
j6S  pages.  Full  Morocco,  Gilt  Edge,  I2.50 

"  Carefully  and  systematically  compiled." — The  London  Lancet. 

"  The  best  condensation  of  the  essentials  of  Practice  I  have  yet  seen.  ...  It  will  be 
an  admirable  review  book  for  students  after  a  solid  course  of  study,  and  it  will  be  scarcely  less 
useful  to  the  busy  practitioner  as  a  ready  means  of  refreshing  his  memory." — C.  A.  Lindsley, 
M.D.,  Professor  of  Theory  and  Practice  of  Medicine,   Yale  College,  New  Haven. 

HUMPHREY.  A  Manual  for  Nurses,  Including  general  Anatomy  and  Physiology, 
management  of  the  sick-room,  etc.  By  Laurence  Humphrey,  m.a.,  m.b., 
M.R.C.S.,  Assistant  Physician  to,  and  Lecturer  at,  Addenbrook's  Hospital,  Cam- 
bridge, England.     Eleventh  Edition.     i2mo.     Illustrated,  Cloth,  $1.25 


MEDICAL  AND  SCIENTIFIC  PUBLICA  TIONS.  15 

HOVELL.  Diseases  of  the  Ear  and  Naso-Pharynx.  A  Treatise  including 
Anatomy  and  Piiysiology  of  the  Organ,  together  with  the  treatment  of  the  affec- 
tions of  the  Nose  and  Pharynx  which  conduce  to  aural  disease.  By  T.  Mark 
HovELL,  F.R.c.s.  (Edin.),  M.R.c.s.  (Eng.),  Aural  Surgeon  to  the  London  Hospital, 
to  Hospital  for  Diseases  of  the  Throat,  and  to  British  Hospital  for  Incurables, 
etc.     122  Illustrations.     Octavo.  Cloth,  Net,  $5.00 

HUTCHINSON.  The  Nose  and  Throat.  A  Manual  of  the  Diseases  of  the  Nose 
and  Throat,  including  the  Nose,  Naso-Pharynx,  Pharynx  and  Larynx.  By 
Procter  S.  Hutchinson,  m.r.c.s.,  Ass't  Surgeon  to  the  London  Hospital  for 
Diseases  of  the  Throat.  Illustrated  by  several  Lithograph  Plates  and  40  other 
Illus.,  many  of  which  have  been  made  from  original  drawings.  i2mo.  Cloth,  $1.25 

JACOBSON.  Operations  of  Surgery.  By  W.  H.  A.  Jacobson,  b.a.  oxon., 
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Children  and  Women,  etc.     With  over  200  lUust.      Cloth,  $5.00  ;  Leather,  $6.00 

Diseases  of  the  Male  Organs  of  Generation.    88  Illustrations.    8vo. 

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KENWOOD.    Public  Health  Laboratory  Work.      By  H.  R.  Kenwood,  m.b., 

D.P.H.,  F.C.S.,  Instructor  in  Hygienic  Laboratory,  University  College,  late  Assistant 

Examiner  in  Hygiene,  Science  and  Art  Department,  South  Kensington,  London, 

etc.     With  116  Illustrations  and  3  Plates.  Cloth,  $3.00 

*4(.*  A  manual  dealing,  in  a  concise  and  practical  manner,  with  those  analyses 

of  Water,  Air,  Food,  etc.,  which  are  especially  related  to  Hygiene,  and  a  knowledge 

of  which  is  valuable  to  the  Public  Health  Student  and  the  Medical  Officer  of  Health. 

The  book  includes  a  brief  account  of  the  more  common  Bacteriological  methods 

employed   in   the   Examination  of  Water,  Air,  Food,  etc.,  by  Rubert  Boyce,  m.b., 

M.R.C.S..,  Assistant  Professor  of  Pathology  in  University  College,  London. 

KIRKES'  Physiology,  [rjth  Authorized  Edltioti.  Just  Ready.  i2mo.  Dark  Red 
Cloth.)  A  Handbook  of  Physiology.  Thirteenth  London  Edition,  Revised  and 
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516  Illustrations,  some  of  which  are  printed  in  Colors.     i2mo. 

Cloth,  $4.00;  Leather,  ^5.00 

KLEEN  AND  HARTWELL.  Handbook  of  Massage.  By  Emil  Kleen,  m.d., 
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Edward  Mussey  Hartwell,  m.d.,  ph.d..  Director  of  Physical  Training  in  the 
Public  Schools  of  Boston.  With  an  Introduction  by  Dr.  S.  Weir  Mitchell, 
of  Philadelphia.  Illustrated  with  a  series  of  Photographs  made  specially  by 
Dr.  Kleen  for  the  American  Edition.     Svo.  Cloth,  $2.j$ 

LANDIS'  Compend  of  Obstetrics  ;  especially  adapted  to  the  Use  of  Students  and 
Physicians.  By  Henry  G.  Landis,  m.d.  Fifth  Edition.  Revised  by  Wm.  H. 
Wells,  Assistant  Demonstrator  of  Clinical  Obstetrics,  Jefferson  Medical  College; 
Member  Obstetrical  Society  of  Philadelphia,  etc.  Enlarged.  With  Many  Illus- 
trations.    No.  ^  ? Quiz- Compend?  Series. 

Cloth,  $1.00;  interleaved  for  the  addition  of  Notes,  $1.25 

LANDOIS.  A  Text-Book  of  Human  Physiology  ;  including  Histology  and  Micro- 
scopical Anatomy,  with  special  reference  to  the  requirements  of  Practical  Medi- 
cine. By  Dr.  L.  Landois,  Professor  of  Physiology  and  Director  of  the  Physio- 
logical Institute  in  the  University  of  Greifswald.  Fourth  American,  translated 
from-the  Seventh  German  Edition,  with  additions,  by  Wm.  Stirling,  m.d.,  d.Sc, 
Brackenbury  Professor  of  Physiology  and  Histology  in  Owen's  College,  and  Pro- 
fessor in  Victoria  University,  Manchester  ;  Examiner  in  Physiology  in  University 
of  Oxford,  England.  With  845  Illustrations,  many  of  which  are  printed  in 
Colors.     Svo.  Cloth,  I7.00 ;  Leather,  $8.00 

"The  MOST  COMPLETE  resume  of  all  the  facts  in  physiology  in  the  language." — The  Lancet. 
"Excellently  clear,  attractive,  and  succinct." — British  Medical  Journal. 


16  P.  BLAKISTON,  SON  (S-  CO:S 

lEE.  The  Microtomist's  Vade  Mecum.  Third  Edition.  A  Handbook  of 
Methods  of  Microscopical  Anatomy.  By  Arthur  Bolles  Lee,  Ass't  in  the  Rus- 
sian Laboratory  of  Zoology,  at  Villefranche-sur-Mer  (Nice).  88 1  Articles.  En- 
larged and  Revised.     Octavo.  Net,  $4.00 

LEFFM ANN'S  Compend  of  Medical  Chemistry,  Inorganic  and  Organic.  In- 
cluding Urine  Analysis.  By  Henry  Leffmann,  m'.d..  Prof,  of  Chemistry  and 
Metallurgy  in  the  Penna.  College  of  Dental  Surgery  and  in  the  Wagner  Free 
Institute  of  Science,  Philadelphia.  No.  10  fQi(iz-Conipe7id?  Series.  Fourth 
Edition.    Rewritten.     >    Cloth,  $1.00.    Interleaved  for  the  addition  of  Notes,  $1.25 

The  Coal-Tar  Colors,  with  Special  Reference  to  their  Injurious  Qualities  and 
the  Restrictions  of  their  Use.  A  Translation  of  Theodore  Weyl's  Mono- 
graph.    i2mo.  Cloth,  $1.25 

Progressive  Exercises  in  Practical  Chemistry.  A  Laboratory  Handbook. 
Illustrated.     Second  Edition,  Revised  and  Enlarged. i2mo.      Cloth,  gi.oo 

LEFFMANN  AND  BEAM.  Examination  of  Water  for  Sanitary  and  Technical 
Purposes.  By  Henry  Leffmann,  m.d..  Professor  of  Chemistry  and  Metallurgy, 
Penna.  College  of  Dental  Surgery,  Hygienist  and  Food  Inspector  Penna.  State 
Board  of  Agriculture,  etc.;  and  William  Beam,  a.m.,  formerly  Chief  Chemist 
B.  &  O.  R.  R.     Second  Edition.     Enlarged.     Illustrated.     i2mo.       Cloth,  $1.25 

Analysis  of  Milk  and  Milk  Products.  Arranged  to  suit  the  needs  of  Analyt- 
ical Chemists,  Dairymen,  and  Milk  Inspectors.     i2mo.  Cloth,  $1.25 

LEGG  on  the  Urine.  Practical  Guide  to  the  Examination  of  Urine.  By  J. 
WiCKHAM  Legg,  m.d.  Seventh  Edition,  Enlarged.  Edited  and  Revised  by  H. 
Lewis  Jones,  m.a.,  m.d.,  m.r.c.p.     Illustrated.     i2mo.  Cloth,  $1.00 

LEWERS.  On  the  Diseases  of  Women.  A  Practical  Treatise.  By  Dr.  A.  H. 
N.  Lewers,  Assistant  Obstetric  Physician  to  the  London  Hospital  ;  and  Phy- 
sician to  Out-patients,  Queen  Charlotte's  Lying-in  Hospital;  Examiner  in  Mid- 
wifery and  Diseases  of  Women  to  the  Society  of  Apothecaries  of  London.  With 
146  Engravings.     Third  Edition,  Revised.  Cloth,  $2.50 

LEWIS  (BEVAN).  Mental  Diseases.  A  text-book  having  special  reference  to  the 
Pathological  aspects  of  Insanity.  By  Bevan  Lewis,  l.h.c.p.,  m.r.c.s..  Medi- 
cal Director,  West  Riding  Asylum,  Wakefield,  England.  18  Lithographic  Plates 
and  other  Illustrations.     8vo.  Cloth,  $6.00 

LINCOLN.    School  and  Industrial  Hygiene.    By  D.  F.  Lincoln,  m.d.    Cloth,  .50 

LIZARS  (JOHN).     On  Tobacco.     The  Use  and  Abuse  of  Tobacco.  Cloth,  .50 

LONGLEY'S  Pocket  Medical  Dictionary  for  Students  and  Physicians.  Giving 
the  Correct  Definition  and  Pronunciation  of  all  Words  and  Terms  in  General 
Use  in  Medicine  and  the  Collateral  Sciences,  with  an  Appendix,  containing 
Poisons  and  their  Antidotes,  Abbreviations  Used  in  Prescriptions,  and  a  Metric 
Scale  of  Doses.     By  Elias  Longley.         Cloth,  $1.00;  Tucks  and  Pocket,  $1.25 

MACNAMARA.  On  the  Eye.  A  Manual.  By  C.  Macnamara,  m.d.  Fifth 
Edition,  Carefully  Revised;  with  Addidons  and  Numerous  Colored  Plates,  Dia- 
grams of  Eye,  Wood-cuts,  and  Test  Types.     Demi  8vo.  Cloth,  $4.00 

MACALISTER'S  Human  Anatomy.  800  Illustrations.  A  New  Text-book  for 
Students  and  Practitioners.  Systematic  and  Topographical,  including  the 
Embryology,  Histology  and  Morphology  of  Man.  With  special  reference  to  the 
requirements  of  Practical  Surgery  and  Medicine.  By  Alex.  Macalister,  m.d., 
F.R.S.,  Professor  of  Anatomy  in  the  University  of  Cambridge,  England;  Examiner 
in  Zoology  and  Comparadve  Anatomy,  University  of  London ;  formerly  Professor 
of  Anatomy  and  Surgery,  University  of  Dublin.  With  816  Illustrations,  400  of 
which  are  original.     Octavo.  Cloth,  $7.50;  Leather,  p. 50 

MACDONALD'S  Microscopical  Examinations  of  Water  and  Air.  With  an  Ap- 
pendix on  the  Microscopical  Examination  of  Air.  By  J.  D.  Macdonald,  m.d. 
25  Lithographic  Plates,  Reference  Tables,  etc.     Second  Ed.     8vo.     Cloth,  $2.75 


MEDICAL  AND  SCIENTIFIC  PUBLICA  TIONS.  17 

MACKENZIE.  The  Pharmacopoeia  of  the  London  Hospital  for  Diseases  of 
the  Throat.  By  Sir  Morell  Mackenzie,  m.d.  Fifth  Edition.  Revised  and 
Improved  by  F.G.  Harvey,  Surgeon  to  the  Hospital.  Cloth,  $1.25 

MACREADY.  A  Treatise  on  Ruptures.  By  Jonathan  F.  C.  H.  Macready, 
F.R.C.S.,  Surgeon  to  the  Great  Northern  Central  Hospital ;  to  the  City  of  London 
Hospital  for  Diseases  of  the  Chest ;  to  the  City  of  London  Truss  Society,  etc. 
With  24  full-page  Lithographed  Plates  and  numerous  Wood-Engravings.  Octavo. 

Cloth,  Net,  $6.00 

MANN,  Forensic  Medicine  and  Toxicology.  A  Text-Book  by  J.  Dixon  Mann, 
M.D,,  F.R.C.P.,  Professor  of  Medical  Jurisprudence  and  Toxicology  in  Owens  Col- 
lege, Manchester ;  Examiner  in  Forensic  Medicine  in  University  of  London,  etc. 
Illustrated.     Octavo.  Cloth,  A^et,  $6.50 

MANN'S  Manual  of  Psychological  Medicine  and  Allied  Nervous  Diseases.  Their 
Diagnosis,  Pathology,  Prognosis  and  Treatment,  including  their  Medico-Legal 
Aspects  ;  with  chapter  on  Expert  Testimony,  and  an  abstract  of  the  laws  relating 
to  the  Insane  in  all  the  States  of  the  Union.  By  Edward  C.  Mann,  m.d., 
member  of  the  New  York  County  Medical  Society.  With  Illustrations  of  Typical 
Faces  of  the  Insane,  Handwriting  of  the  Insane,  and  Micro-photographic  Sec- 
tions of  the  Brain  and  Spinal  Cord.  Octavo.  Cloth,  $5-oo 
MARSHALL'S  Physiological  Diagrams,  Life  Size,  Colored.  Eleven  Life-size 
Diagrams  (each  7  feet  by  3  feet  7  inches).  Designed  for  Demonstration  before 
the  Class.  By  John  Marshall,  f.r.s.,  f.r.c.s.,  Professor  of  Anatomy  to  the 
Royal  Academy  ;  Professor  of  Surgery,  University  College,  London,  etc. 

In  Sheets  Unmounted,  A'ei,  $40.00 
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No.  4 — The  Heart  and  Principal  Blood-vessels.  No.  5 — The  Lymphatics  or  Absorb- 
ents. No.  6 — The  Digestive  Organs.  No.  7 — The  Brain  and  Nerves.  Nos.  8  and  9 — 
The  Organs  of  the  Senses.  Nos.  10  and  11 — The  Microscopic  Structure  of  the 
Textures  and  Organs.     {Send for  Special  Circular.) 

MARSHALL  &  SMITH.  On  the  Urine.  The  Chemical  Analysis  of  the  Urine. 
By  John  Marshall,  m.d.,  and  Prof.  Edgar  F.  Smith,  of  the  Chemical  Labora- 
tories, University  of  Pennsylvania.  Phototype  Plates.  i2mo.  Cloth,  $1.00 
MASON'S  Compend  of  Electricity,  and  its  Medical  and  Surgical  Uses.  By 
Charles  F.  Mason,  m.d..  Assistant  Surgeon  U.  S.  Army.  With  an  Intro- 
duction by  Charles  H.  May,  m.d..  Instructor  in  the  New  York  Polyclinic. 
Numerous  Illustrations.  i2mo.  Cloth,  $1.00 
McBRIDE.  Diseases  of  the  Throat,  Nose  and  Ear.  A  Clinical  Manual  for  Stu- 
dents and  Practitioners.  By  P.  McBride,  m.d.,  f.r.c.p.  (Edin.),  Surgeon  to  the 
Ear  and  Throat  Department  of  the  Royal  Infirmary;  Lecturer  on  Diseases  of 
Throat  and  Ear,  Edinburgh  School  of  Medicine,  etc.  With  Colored  Illustrations 
from  Original  Drawings.    2d  Edition.    Octavo.       Handsome  Cloth,  Gilt  top,  $7.00 

MAXWELL.  Terminologia  Medica  Polyglotta.  By  Dr.  Theodore  Maxwell, 
assisted  by  others  in  various  countries.     8vo.  Cloth,  $4.00 

The  object  of  this  work  is  to  assist  the  medical  men  of  any  nationality  in  reading  medical  literature  written 
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Italian,  Spanish,  Russian  aed  Latin. 

MAYS'  Therapeutic  Forces  ;  or.  The  Action  of  Medicine  in  the  Light  of  the  Doc- 
trine of  Conservation  of  Force.     By  Thomas  J.  Mays,  m.d.  Cloth,  $1.25 
Theine  in  the  Treatment  of  Neuralgia.    lemo.                       yi  bound,  .50 


18  P.  BLAKISTON,  SON  &^  CO:S 


MEDICAL  Directory  of  Philadelphia  and  Camden,  1889.  Containing  lists  of 
Physicians  of  all  Schools  of  Practice,  Dentists,  Veterinarians,  Druggists  and 
Chemists,  with  information  concerning  Medical  Societies,  Colleges  and  Associa- 
tions, Hospitals,  Asylums,  Charities,  etc.  Morocco,  Gilt  edges,  $2.50 

MEIGS.  Milk  Analysis  and  Infant  Feeding.  A  Treatise  on  the  Examination  of 
Human  and  Cows'  Milk,  Cream,  Condensed  Milk,  etc.,  and  Directions  as  to  the 
Diet  of  Young  Infants.     By  Arthur  V.  Meigs,  m.d.     i2mo.  Cloth,  $1.00 

MEMMINGER.  Diagnosis  by  the  Urine.  The  Practical  Examination  of  Urine, 
with  Special  Reference  to  Diagnosis.  By  Allard  Memminger,  m.d..  Professor 
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50 


i<  .,      1         f  Jan.  to  June)                         ,,         „  ^  -^ 

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Edition.      Authorized   Translation   by  Edgar  F.  Smith,  m.a.,  ph.d.,  Prof,  of 

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Letter-press  Explanations  and  References.     One  Volume.  Cloth,  $5.00 


MEDICAL  AND  SCIENTIFIC  PUBLICA  TIONS.  23 

SANSOM.  Diseases  of  The  Heart.  The  Diagnosis  of  Diseases  of  the  Heart  and 
Thoracic  Aorta,  and  the  Pathology  which  serves  for  the  recognition  of  Morbid 
States  of  the  Organs  of  Circulation.  By  A.  Ernest  Sansom,  m.d.,  f.r.c.p., 
Physician  to  the  London  Hospital,  Examiner  in  Medicine  Royal  College  of 
Physicians,  etc.     With  Plates  and  other  Illustrations.     8vo.  Cloth,  $7.50 

SAYRE.  Organic  Materia  Medica  and  Pharmacognosy.  A  Handbook  for 
Students  of  Pharmacy  and  Medicine.  By  L.  E.  Sayre,  ph.g.,  Professor  of 
Pharmacy  and  Materia  Medica  in  the  University  of  Kansas,  Member  of  the 
Committee  of  Revision  of  the  U.  S.  Pharmacopoeia,  1890.  500  Illustrations, 
many  of  which  are  original.     Svo.  Cloth,  $4.50 

SCHULTZE.  Obstetrical  Diagrams.  Being  a  Series  of  20  Colored  Lithograph 
Charts,  imperial  map  size,  of  Pregnancy  and  Midwifery,  with  accompanying 
explanatory  (German)  text,  illustrated  by  wood-cuts.  By  Dr.  B.  S.  Schultze, 
Professor  of  Obstetrics,  University  of  Jena.     Second  Revised  Edition. 

Price,  in  Sheets,  iAW,  $26.00 ;  Mounted  on  Rollers,  Muslin  Backs,  N^et,  $36.00 

SEWELL.  Dental  Surgery,  including  Special  Anatomy  and  Surgery.  By  Henry 
Sewell,  M.R.C.S.,  L.D.S.,  President  Odontological  Society  of  Great  Britain.  3d 
Edition,  greatly  enlarged,  with  about  200  Illustrations.  Cloth,  I3.00 

SHAWE.  Notes  for  Visiting  Nurses,  and  all  those  interested  in  the  working  and 
organization  of  District,  Visiting,  or  Parochial  Nurse  Societies.  By  Rosilind 
Gillette  Shawe,  District  Nurse  for  the  Brooklyn  Red  Cross  Society.  With  an 
Appendix  explaining  the  organization  and  working  of  various  Visiting  and  Dis- 
trict Nurse  Societies,  by  Helen  C.  Jenks,  of  Philadelphia.    i2mo.    Cloth,  $1.00 

SMITH.  Abdominal  Surgery.  Being  a  Systematic  Description  of  all  the  Princi- 
pal Operations.  By  J.,Greig  Smith,  M.A.,  f.r.s.e.,  Surg,  to  British  Royal  In- 
firmary ;  Lecturer  on  Surgery,  Bristol  Medical  School ;  Late  Examiner  in  Surgery, 
University  of  Aberdeen,  etc.    Over  80  Illustrations.    Fourth  Edition.    Cloth,  $7.00 

SMITH.  Electro-Chemical  Analysis.  By  Edgar  F.  Smith,  Professor  of  Chem- 
istry, Liniversity  of  Pennsylvania.  Second  Edition,  Revised  and  Enlarged.  28 
Illustrations.     i2mo.  Cloth,  $1.25 

SMITH  AND  KELLER.  Experiments.  Arranged  for  Students  in  General  Chem- 
istry. By  Edgar  F.  Smith,  Professor  of  Chemistry,  University  of  Pennsylvania, 
and  Dr.  H.  F.  Keller,  Professor  of  Chemistry,  Philadelphia  High  School.  Sec- 
ond Edition.     Svo.     Illustrated.  Cloth,  Net,  .60 

STAMMER.  Chemical  Problems,  with  Explanations  and  Answers.  By  Karl 
Stammer.  Translated  from  the  2d  German  Edition,  by  Prof.  W.  S.  Hoskinson, 
A.M.,  Wittenberg  College,  Springfield,  Ohio.     i2mo.  Cloth.  .75 

STARR.  The  Digestive  Organs  in  Childhood.  Second  Edition.  The  Diseases 
of  the  Digestive  Organs  in  Infancy  and  Childhood.  With  Chapters  on  the 
Investigation  of  Disease  and  the  Management  of  Children.  By  Louis  Starr, 
M.D.,  late  Clinical  Prof,  of  Diseases  of  Children  in  the  Hospital  of  the  University 
of  Penn'a;  Physician  to  the  Children's  Hospital,  Phila.  Second  Edition. 
Revised  and  Enlarged.  Illustrated  by  two  Colored  Lithograph  Plates  and 
numerous  wood-engravings.     Crown  Octavo.  Cloth,  $2.25 

The  Hygiene  of  the  Nursery,  including  the  General  Regimen  and  Feed- 
ing of  Infants  and  Children,  and  the  Domestic  Management  of  the  Ordinary 
Emergencies  of  Early  Life,  Massage,  etc.  Fourth  Edidon.  Enlarged.  25 
Illustrations.     i2mo.     280  pages.  Cloth,  $1.00 

See  also  Goodhart  and  Starr.    Pa^e  11. 


24  P.  BLAKISTON,  SON  &^  CO:S 

STARLING.  Elements  of  Human  Physiology.  By  Ernest  H.  Starling,  m.d. 
LoxD.,  M.  R.  c.  P.,  Joint  Lecturer  on  Physiology  at  Guy's  Hospital,  London; 
Member  of  Physiological  Society,  etc.  With  loo  Illustrations.  i2mo.  437 
pages.  Cloth,  ;j52.oo 

STEARNS.  Mental  Diseases.  Lectures  on  Mental  Diseases,  designed  especially  for 
Medical  Students  and  General  Practitioners.  By  Henry  Putnam  Stearns,  m.d.. 
Physician  Superintendent  at  the  Hartford  Retreat,  Lecturer  on  Mental  Diseases 
in  Yale  University,  Member  of  the  American  Medico-Psychological  Ass'n,  Hon- 
orary Member  of  the  Boston  Medico- Pyschological  Society.  With  a  Digest  of 
Laws  of  the  Various  States  Relating  to  Care  of  Insane.  Illustrated.  New  Series 
of  Manuals.  Cloth,  $3.00;  Sheep,  $3.50 

STEAVENSON  AND  JONES.  Medical  Electricity.  A  Practical  Handbook  for 
Students  and  Practitioners  of  Medicine.  By  W.  E.  Steavenson,  m.d.,  late  in 
charge  Electrical  Department,  St.  Bartholomew's  Hospital,  and  H.  Lewis  Jones, 
M.A.,  M.D.,  M.R.C.P.,  Medical  Officer  in  Charge  Electrical  Department,  St.  Bar- 
tholomew's Hospital.     103  Illustrations.     i2mo.  Cloth,  $2.50 

STEVENSON  AND  MURPHY.    A  Treatise  on  Hygiene.    By  Various  Authors. 
Edited  by  Thomas  Stevenson,  m.d.,  f.r.c.p..  Lecturer  on  Chemistry  and  Medi- 
cal Jurisprudence  at  Guy's    Hospital,  London,  etc.,  and  Shirley  F.  Murphy, 
Medical  Officer  of  Health  to  the  County  of  London,     In  Two  Octavo  Volumes. 
Vol.1.    loi 3  pages.  With  Plates  and  Wood  Engravings.    Octavo.    Cloth,  $7.50 
Vol.  II.     With  Plates  and  Wood  Engravings.     Octavo. 

Just  Ready.     Cloth,  $7.50 
:^:^  Special  Circular  upon  applicatioji. 

STEWART'S  Compend  of  Pharmacy.  Based  upon  "  Remington's  Text-Book  of 
Pharmacy."  By  F.  E.  Stewart,  m.d.,  ph.g..  Quiz  Master  in  Chem.  and  Theoreti- 
cal Pharmacy,  Phila.  College  of  Pharmacy;  Lect.  in  Pharmacology,  Jefferson 
Medical  College.  4th  Ed.  Revised  in  accordance  with  U.  S.  P.,  1890.  Com- 
plete tables  of  Metric  and  English  Weights  and  Measures,  f  Quiz- Compend? 
Series.  Cloth,  $1.00;  Interleaved  for  the  addition  of  notes,  $1.25 

STIRLING.  Outlines  of  Practical  Physiology.  Including  Chemical  and  Experi- 
mental Physiology,  with  Special  Reference  to  Practical  Medicine.  By  W.  Stir- 
ling, M.D.,  Sc.D.,  Prof,  of  Phys.,  Owens  College,  Victoria  University,  Manchester. 
Examiner  in  Honors  School  of  Science,  Oxford,  England.  Second  Edition. 
234  Illustrations.  Cloth,  $3.00 

Outlines  of  Practical  Histology.  368  Illustrations.  Second  Edition.  Re- 
vised and  Enlarged  with  new  Illustrations.     i2mo.  Cloth,  $3.00 

STOCKEN'S  Dental  Materia  Medica.  Dental  Materia  Medica  and  Therapeutics, 
with  Pharmacopoeia.     By  James  Stocken,  d.d.s.     Third  Edition.     Cloth,  $2.50 

STRAHAN.  Extra-Uterine  Pregnancy.  The  Diagnosis  and  Treatment  of  Extra- 
Uterine  Pregnancy.  Being  the  Jenks  Prize  Essay  of  the  College  of  Physicians 
of  Philadelphia.  By  John  Strahan,  m.d.  (Univ.  of  Ireland),  late  Res.  Surgeon 
Belfast  Union  Infirmary  and  Fever  Hospital.     Octavo.  Cloth,  .75 

SUTTON.  Lectures  on  Pathology.  Delivered  at  the  London  Hospital  by  the  late 
Henry  Gawen  Sutton,  m.b.,  f.r.c.p..  Physician  and  Lecturer  on  Pathology  at 
the  London  Hospital.  Edited  by  Maurice  E.  Paul,  m.d.,  and  Revised  by  Samuel 
WiLKS,  M.D.,  ll.d.,  f.r.s.     Octavo.     503  pages.  Cloth,  $4.50 

SWANZY.  Diseases  of  the  Eye  and  their  Treatment.  A  Handbook  for  Physi- 
cians and  Students.  By  Henry  R.  Swanzy,  a.m.,  m.b.,  f.r.c.s.i..  Surgeon  to 
the  National  Eye  and  Ear  Infirmary  ;  Ophthalmic  Surgeon  to  the  Adelaide  Hos- 
pital, Dublin.  Fourth  Edition,  Thoroughly  Revised.  Enlarged.  164  Illustra- 
tions. Two  Colored  and  one  Plain  Plate,  and  a  Zephyr  Test  Card.  i2mo. 
New  Series  of  Manuals.  <       Cloth,  $3.00;  Sheep,  $3.50 


MEDICAL  AND  SCIEi\TlFIC  PUBLICATIONS.  25 

SUTTON'S  Volumetric  Analysis.  A  Systematic  Handbook  for  the  Quantitative 
Estimation  of  Chemical  Substances  by  Measure,  Applied  to  Liquids,  Solids  and 
Gases.  By  Francis  Sutton,  f.c.s.  Sixth  Edition,  Revised  and  Enlarged, 
with  Illustrations.     8vo.  Cloth,  $5.00 

SYMONLS.  Manual  of  Chemistry,  for  Medical  Students.  By  Brandreth 
Symonds,  a.m.,  M.D.,  Ass't  Physician  Roosevelt  Hospital,  Out-Patient  Department ; 
Attending  Physician  Northwestern  Dispensary,  New  York.  Second  Edition. 
l2mo.  Cloth,  $2.00 

TAFT'S  Operative  Dentistry.  A  Practical  Treatise  on  Operative  Dentistry.  By 
Jonathan  Taft,  d.d.s.  Fourth  Revised  and  Enlarged  Edition.  Over  100  Il- 
lustrations.    8vo.  Cloth,  $4.25  ;  Leather,  $5.00 

Index  of  Dental  Periodical  Literature.    8vo.  Cloth,  $2.00 

TALBOT.  Irregularities  of  the  Teeth,  and  Their  Treatment.  By  Eugene  S. 
Talbot,  m.d..  Professor  of  Dental  Surgery  Woman's  Medical  College,  and 
Lecturer  on  Dental  Pathology  in  Rush  Medical  College,  Chicago.  Second  Edi- 
tion, Revised  and  Enlarged  by  about  100  pages.  Octavo.  234  Illustrations 
(169  of  which  are  original).     261  pages.  Cloth,  $3.00 

TANNER'S  Memoranda  of  Poisons  and  their  Antidotes  and  Tests.  By  Thos. 
Hawkes  Tanner,  m.d.,  f.r.c.p.  7th  American,  from  the  Last  London  Edition. 
Revised  by  John  J.  Reese,  m.d..  Professor  Medical  Jurisprudence  and  Toxi- 
cology in  the  University  of  Pennsylvania.     i2mo.  Cloth,  .75 

TAYLOE.  Practice  of  Medicine.  A  Manual.  By  Frederick  Taylor,  m.d., 
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Evelina  Hospital  for  Sick  Children,  and  Examiner  in  Materia  Medica  and  Phar- 
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THOMPSON.  Urinary  Organs.  Diseases  of  the  Urinary  Organs.  Containing  32 
Lectures.  By  Sir  Henry  Thompson,  f.r.c.s..  Emeritus  Professor  of  Clinical  Sur- 
gery in  University  College.  Eighth  London  Ed.  Octavo.  470  pages.    Cloth,  $3.50 

Calculous  Diseases.     The  Preventive  Treatment  of  Calculous  Disease,  and 
the  Use  of  Solvent  Remedies.     Third  Edition.        i6mo.  Cloth,  $1.00 

THORBURN.  Surgery  of  the  Spinal  Cord.  A  Contribution  to  the  study  of.  By 
William  Thorburn,  b.Sc,  m.d.     Illustrated.     Octavo.  Cloth,  $4- 5° 

THORNTON.    The  Surgery  of  the  Kidney.    By  John  Knowslev  Thornton, 

M.B.  Edin.     With  19  Illustrations.  Cloth,  $1.75 

TOMES'  Dental  Anatomy.    A  Manual  of  Dental  Anatomy,  Human  and  Compara- 
tive.    By  C.  S.  Tomes,  d.d.s.     235  Illustrations.     4th  Ed.     i2mo.      Cloth,  $4.00 
Dental  Surgery.    A  System  of   Dental  Surgery.    By  John  Tomes,  f.r.s. 
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292  Illustrations.     i2mo.     772  pages.  Cloth,  $5.00 

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26  P.  BLAKISTON,  SON  &-  CO.'S 

TREVES.  German-Eng-lish  Medical  Dictionary.    By  Frederick  Treves,  f.r.c.s., 

assisted  by  Dr.  Hugo  Lang,  b.a.  (Munich).     i2mo.  }4  Russia,  $3.75 

Physical  Education,  Its  Effects,  Value,  Methods,  etc.  Cloth,  $1 .25 

TRIMBLE.  Practical  and  Analytical  Chemistry.  Being  a  complete  course  in 
Chemical  Analysis.  By  Henry  Trimble,  ph.m.,  Professor  of  Analytical  Chem- 
istry in  the  Philadelphia  College  of  Pharmacy.  Fourth  Edition.  Enlarged. 
Illustrated.     8vo.  Cloth,  $1.50 

TURNBULL'S  Artificial  Anaesthesia.  The  Advantages  and  Accidents  of  Artifi- 
cial Anaesthesia  ;  Its  Employment  in  the  Treatment  of  Disease;  Modes  of  Ad- 
ministration ;  Considering  their  Relative  Risks ;  Tests  of  Purity  ;  Treatment  of 
Asphyxia;  Spasms  of  the  Glottis;  Syncope,  etc.  By  Laurence  Turnbull,  m.d., 
PH.  G.,  Aural  Surgeon  to  Jefferson  College  Hospital,  etc.  Third  Edition,  Re- 
vised and  Enlarged.     40  Illustrations.     i2mo.  Cloth,  $3.00 

TUKE.  Dictionary  of  Psychological  Medicine.  Giving  the  Definition,  Ety- 
mology, and  Synonyms  of  the  terms  used  in  Medical  Psychology,  with  the 
Symptoms,  Pathology,  and  Treatment  of  the  recognized  forms  of  Mental  Dis- 
orders, together  with  the  Law  of  Lunacy  in  Great  Britain  and  Ireland.  Edited  by 
D.  Hack  Tuke,  m.d.,ll.d..  Examiner  in  Mental  Physiology  in  the  University 
of  London.     Two  Volumes.     Octavo.  Cloth,  $13.00 

TUSON.     Veterinary  Pharmacopoeia,  including  the  outlines  of  Materia  Medica 
and  Therapeutics.     By  Richard  V.  Tuson,  late  Professor  at  the  Royal  Veter- 
inary College.     Fifth  Edition,  by  Prof.  Bayxe.     i2mo.  In  Press. 
TYSON.    Bright's  Disease  and  Diabetes.    With  Especial  Reference  to  Pathology 
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Disease.    With  Colored  Plates  and  many  Wood  Engravings.    8vo.     Cloth,  $3.50 
Guide  to  the  Examination  of  Urine.     Eighth  Edition.     For  the  Use  of 
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Handbook  of  Physical  Diagnosis.    Illustrated.    2d  Ed.    i2mo.    Cloth,  $1.50 

UNITED  STATES  PHARMACOPOEIA.  1890.  Seventh  Decennial  Revision. 
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Envelope.  .25 

VAN  HARLINGEN  on  Skin  Diseases.  A  Practical  Manual  of  Diagnosis  and 
Treatment.  By  Arthur  Van  Harlingen,  m.d..  Professor  of  Diseases  of  the 
Skin  in  the  Philadelphia  Polyclinic ;  Clinical  Lecturer  on  Dermatology  at  Jef- 
ferson Medical  College.  Third  Edition.  Revised  and  Enlarged.  With  Formulae 
and  many  Illustrations.  /;/  Press. 

VAN  NUYS  on  The  Urine.  Chemical  Analysis  of  Healthy  and  Diseased  Urine, 
Qualitative  and  Quantitative.  By  T.  C.  Van  Nuys,  Professor  of  Chemistry- 
Indiana  University.     39  Illustrations.     Octavo.  Cloth,  $1.00 

VOSWINKEL.  Surgical  Nursing.  A  Manual  for  Nurses.  By  Bertha  M.  Vos- 
winkel.  Children's  Hospital,  Columbus,  O.     Illustrated.  /n  Press. 

VIRCHOW'S  Post-mortem  Examinations.  A  Description  and  Explanation  of  the 
Method  of  Performing  them  in  the  Dead  House  of  the  Berhn  Charite  Hospital, 
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lated by  Dr.  T.  P.  Smith.     Third  Edition,  with  Additions.  Cloth,  $1.00 


MEDICAL  AND  SCIENTIFIC  PUBLICA  TIONS.  27 

WALSHAM.  Manual  of  Practical  Surgery.  For  Students  and  Physicians.  By 
Wm.  J.  Walsham,  M.D.,  F.R.C.S,,  Ass't  Surg.  to,  and  Dem.  of  Practical  Surg,  in, 
St.  Bartholomew's  Hospital,  Surg,  to  Metropolitan  Free  Hospital,  London. 
Third  Edition,  Revised  and  Enlarged.  With  318  Engravings.  New  Series  of 
Manuals.  Cloth,  $3.00  ;  Leather,  $3.50 

WARING.  Practical  Therapeutics.  A  Manual  for  Physicians  and  Students.  By 
Edward  J.  Waring,  m.d.  Fourth  Edition,  Revised,  Rewritten  and  Rearranged 
by  Dudley  W.  Buxton,  m.d..  Assistant  to  the  Professor  of  Medicine,  University 
College,  London.     Crown  Octavo.  Cloth,  $3.00;  Leather,  $3.50 

WARREN.  Compend  Dental  Pathology  and  Dental  Medicine.  Containing  all 
the  most  noteworthy  points  of  interest  to  the  Dental  Student  and  a  Chapter 
on  Emergencies.  By  Geo.  W.  Warren,  d.d.s..  Clinical  Chief,  Penn'a  College 
of  Dental  Surgery,  Phila.  Second  Edition,  Enlarged.  Illustrated.  Beiti^  No. 
ij  f  Quiz- Compend  f  Series.     i2mo.  Cloth,  $1.00 

Interleaved  for  the  addition  of  Notes,  $1.25 

Dental  Prostheses  and  Metallurgy.     129  Illustrations.  Cloth,  $1.50 

WATSON  on  Amputations  of  the  Extremities  and  Their  Complications.  By 
B.  A.  Watson,  a.m.,  m.d..  Surgeon  to  the  Jersey  City  Charity  Hospital  and  to 
Christ's  Hospital,  Jersey  City,  N.  J.     250  Illustrations.  Cloth,  $5.50 

Concussions.  An  Experimental  Study  of  Lesions  arising  from  Severe  Con- 
cussions.    8vo.  Paper  cover,  $1.00 

WATTS'  Inorganic  Chemistry.  A  Manual  of  Chemistry,  Physical  and  Inorganic. 
(Being  the  14th  Edition  of  Fowne's  Physical  and  Inorganic  Chemistry.) 
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trations.    i2mo.     595  pages.  Cloth,  $2.25 

Organic  Chemistry.  Second  Edition.  By  Wm.  A,  Tilden,  d.sc,  f.r.s. 
(Being  the  13th  Edition  of  Fowne's  Organic  Chemistry.)  Illustrated. 
i2mo.  ,  Cloth,  $2.25 

WELLS.  Compend  of  Gynecology.  By  Wm.  H.  Wells,  m.d.,  Assistant  Demon- 
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?  Qiiiz-CoDipend?  Series  No.  7.     l2mo.    Cloth,  $1.00  ;  Interleaved  for  Notes,  $1.25 

WESTLAND.  The  Wife  and  Mother.  A  Handbook  for  Mothers.  By  A. 
Westland,  m.d.,  late  Resident  Physician,  Aberdeen  Royal  Infirmary.   CIo.  $2.00 

WETHERED.  Medical  Microscopy.  A  Guide  to  the  Use  of  the  Microscope  in 
Practical  Medicine.  By  Frank  J.  Wethered,  m.d  ,  m.r.c.p.,  Demonstrator  of 
Practical  Medicine,  Middlesex  Hospital  Medical  School,  Assistant  Physician, 
late  Pathologist,  City  of  London  Hospital  for  Diseases  of  Chest,  etc.  With  100 
Illustrations.     i2mo.  Cloth,  $2.50 

WEYL.  Sanitary  Relations  of  the  Coal-Tar  Colors.  By  Theodore  Weyl. 
Authorized  Translation  by  Henry  Leffmann,  m.d.,  ph.d.  This  work  contains 
the  most  recent  trustworthy  information  on  the  physiological  action  of  the  coal- 
tar  colors.  Tests  for  recognizing  the  different  colors  are  given.  A  summary  of 
the  appropriate  legislative  enactments  in  the  leading  countries  in  Europe  is  also 
presented.  The  book  is  believed  to  be  the  only  compilation  in  the  field  in 
Englisli,  and  will  be  found  highly  useful  in  determining  the  permissibility  of  the 
coal- tar  colors,  now  so  much  used  in  articles  of  food  and  drink.  i2mo.  154 
pages.  Cloth,  $1.25 

WHITE.    The  Mouth  and  Teeth.    By  J.  W.  White,  m.d.,  d.d.s.  Cloth.  .50 


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WHITE  AND  WILCOX.    Materia  Medica,  Pharmacy,  Pharmacology,  and 

Therapeutics.  A  Handbook  for  Students.  By  W.  Hale  White,  m.d.,  f.r.c.p., 
etc.,  Physician  to  and  Lecturer  on  Materia  Medica,  Guy's  Hospital;  Examiner  in 
Materia  Medica,  Royal  College  of  Physicians,  London,  etc.  Second  American 
Edition.  Revised  by  Reynold  W.  Wilcox,  m.a.,  m.d.,  ll.d.,  Professor  of  Clin- 
ical Medicine  and  Therapeutics  at  the  New  York  PostGraduate  Medical  School 
and  Hospital ;  Visiting  Physician  St.  Mark's  Hospital ;  Assistant  Visiting  Physi- 
cian Bellevue  Hospital.     Second  Edition,  thoroughly  Revised.     i2mo. 

Cloth,  $3.00;  Leather,  $3.50 

WILSON.  Handbook  of  Hygiene  and  Sanitary  Science.  By  George  Wilson, 
M.A.,  M.D.,  F.R.S.E.,  Medical  Officer  of  Health  for  Mid-Warwickshire,  England. 
With  Illustrations.    Seventh  Edition,  Enlarged  by  200  pages.    i2mo.    Cloth,  $3.25 

WILSON.  The  Summer  and  its  Diseases.  By  James  C.  Wilson,  m.d..  Prof,  of  the 
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WILSON.  System  of  Human  Anatomy,  i  ith  Revised  Edition.  Edited  by  Henry 
Edward  Clark,  m.d.,  m.r.c.s.  492  Illustrations,  26  Colored  Plates,  and  a 
Glossary  of  Terms.     Thick  i2mo.  Cloth,  ;j;6.oo 

WINCKEL.  Diseases  of  Women.  Second  Edition.  Including  the  Dis- 
eases of  the  Bladder  and  Urethra.  By  Dr.  F.  Winckel,  Professor  of 
Gynaecology,  and  Director  of  the  Royal  University  Clinic  for  Women,  in  Munich. 
Translated  by  special  authority  of  Author  and  Publisher,  under  the  supervision 
of,  and  with  an  Introduction  by,  Theophilus  Parvin,  m.d.,  Professor  of 
Obstetrics  and  Diseases  of  Women  and  Children  in  Jefferson  Medical  Col- 
lege, Philadelphia.  With  152  Engravings  on  Wood,  most  of  which  are  original, 
2d  Edition,  Revised  and  Enlarged.  Cloth,  1:3.00;  Leather,  $3.50 

"  Winckel's  hand-book  is  a  work  that  will  be  profitably  consulted  by  all  classes  of  gynecol- 
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work  of  its  kind  in  the  English  language  that  we  are  acquainted  with.  .  .  .  As  a  text-book 
for  students,  as  well  as  a  work  of  reference  for  the  practitioner,  we  can  conscientiously  recom- 
mend Winckel's  '  Diseases  of  Women.'  " — T7ie  Medical  Record. 

Text-Book  of  Obstetrics ;  Including  the  Pathology  and  Therapeutics  of  the 
Puerperal  State.  Authorized  Translation  by  J.  Clifton  Edgar,  a.m.,  m.d., 
Adjunct  Professor  to  the  Chair  of  Obstetrics,  MedicalDepartment,  University 
City  of  New  York.  With  nearly  200  Handsome  Illus.,  the  majority  of  which 
are  original  with  this  work.     Octavo.  Cloth,  $6.00;  Leather,  $7.00 

WOAKES.  Post-Nasal  Catarrh  and  Diseases  of  the  Nose,  causing  Deafness.  By 
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Diseases  of  the  Throat  and  Chest.     26  Illustrations.  Cloth,  $1.50 

WOLFF.  Manual  of  Applied  Medical  Chemistry  for  Students  and  Practitioners  of 
Medicine.  By  Lawrence  Wolff,  m.d.,  Demonstrator  of  Chemistry  in  Jeffer- 
son Medical  College,  Philadelphia.  Cloth,  $1.00 

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of  Nervous  Diseases,  University  of  Pennsylvania,     i2mo.  Cloth,  .50 

WOODY.  Essentials  of  Chemistry  and  Urinalysis.  By  Sam  E.  Woody,  a.m., 
m.d..  Professor  of  Chemistry  and  Public  Hygiene,  and  Clinical  Lecturer  on 
Diseases  of  Children,  in  the  Kentucky  School  of  Medicine.  Third  Edition. 
Illustrated.     i2mo.  Cloth,  $1.25 

WYTHE.  Dose  and  Symptom  Book.  The  Physician's  Pocket  Dose  and  Symptom 
Book.  Containing  the  Doses  and  Uses  of  all  the  Principal  Articles  of  the 
Materia  Medica,  and  Officinal  Preparations.  By  Joseph  H.  Wythe,  a.m.,  m.d. 
17th  Edition,  Revised.  Cloth,  $1.00;  Leather,  with  Tucks  and  Pocket,  $1.25 

YEO'S  Manual  of  Physiology.  Sixth  Edition.  A  Text-book  for  Studeirts  of 
Medicine.  By  Gerald  F.  Yeo.,  m.d.,  f.r.c.s..  Professor  of  Physiology  in  King's 
College,  London.  Sixth  Edition ;  revised  and  enlarged  by  the  author.  With 
254  Wood  Engravings  and  a  Glossary.  Crowij  Octavo.  Being  No.  4,  New 
Series  of  Manuals,  Cloth,  $3.00;  Leather,  $3.50 


MORRIS'S 

HUMAN  ANATOMY. 

A   NEW  TEXT=BOOK. 

791  Illustrations,  214  of  which  are  Printed  in  Several  Colors,  and  most  of 
which  are  original.     OCTAVO.      1200  PAGES. 

Handsome  Cloth,  $7.50 ;    Full  Sheep,  $8.50 ;    Half  Russia, 
Marbled  Edges,  $9.50. 


We  will  send  free  to  any  address  a  large  descriptive  circular 
of  Morris's  Anatomy  giving  sample  pages  and  colored  illustrations,  as 
well  as  a  large  number  of  recommendations  from  prominent  professors 
and  demonstrators,  and  reviews  taken  from  the  best  medical  journals. 


"  The  treatise  on  '  Human  Anatomy '  just  issued  from  the  press  of  Messrs. 
Blakiston  will  be  an  event  of  interest  to  medical  students.  The  first  necessity 
to  the  aspirant  for  a  medical  career  is  the  possession  of  a  complete  and  sys- 
tematic manual  of  anatomy.  The  volume  before  us  is  admirable  in  every  way. 
It  is  magnificently  illustrated  in  colors,  and  a  specially  valuable  feature  is 
the  mode  of  describing  the  illustrations  in  the  text,  which  almost  amounts  to 
a  demonstration.  The  different  sections  have  been  compiled  by  authors  spe- 
cially qualified  for  the  duties  they  assume.  The  illustrations  have  all  been  cut 
on  wood  from  drawings  made  by  special  artists.  The  reading  matter  is 
terse  and  forcible.     The  superfluous  has  been  rigorously  suppressed. 

"The  student  searching  for  a  manual  with  which  to  begin  his  medical 
studies  should  certainly  consider  the  claims  of  this  handsome  volume  before 
committing  himself  irrevocably  to  any  particular  standard  text-book." — The 
Physician  and  Surgeon,  Ann  Arbor,  Mich. 


AN   EMINENTLY   PRACTICAL   BOOK. 

Moullin's  Surgery, 

Second  Edition,  Enlarged. 

A  Complete  Practical  Treatise  on  Surgery,  with  Special  Reference  to  Treatment. 

By  C.  W.  MANSELL  MOULLIN,  M.A.,  M.D.  Oxon.,  F.R.C.S., 

Surgeon  and  Lecturer  on  Physiology  to  the  London  Hospital,  etc. 


Second  American   Edition, 

Edited  by  JOHN  B.  HAMILTON,  M.D.,  LL.D., 

Professor  of  the  Principles  of  Surgery  and  Clinical  Surgery,  Rush  Medical  College,  Chicago  ;   Professor  of 

Surgery;  Chicago   Polyclinic  :   Formerly  Supervising  Surgeon-General,  U.  S.  Marine  Hospital 

Service;  Surgeon  to  Presbyterian  Hospital,  St.  Joseph's  Hospital,  and  Central 

Free  Dispensary,  Chicago,  etc. 

About  Six  Hundred  Illustrations, 

Over  two  hundred  of  which  are  original  with  this  work,  and  many  of  which  are 
printed  in  several  colors. 

Royal  Octavo.    1200  Pages.    Handsome  Cloth,  $7.00  ;  Leather,  Raised  Bands, 
$8.00 ;   Half  Russia,  Crushed,  Marble  Edges,  $9.00. 

These  Prices  are  Absolutely  net. 

Of  the  600  illustrations  over  two  hundred  have  been  specially  prepared  for  this 
work,  and  their  originality  adds  great  value  to  their  usefulness  and  at  the  same  time  exemplifies 
the  character  of  the  whole  book,  in  that  it  has  been  worked  up  from  modern  ideas  and  methods 
instead  of  being  a  mere  rehash  of  the  sayings  and  doings  of  others.  The  illustrations  will  excite 
particular  attention  on  account  of  their  practical  bearing  on  useful  points  in  Surgery.  By  the 
addition  of  colors  to  many  of  these  the  text  is  thoroughly  elucidated,  impressing  at  once  upon 
the  mind  of  the  Surgeon  or  Student  the  real  relations  of  important  parts  of  the  Anatomy,  and 
certain  particular  diagnostic  features.  This  is  especially  patent  in  the  article  on  tumors,  where 
the  illustrations  of  sections  of  the  various  growths  have  been  colored  so  as  to  bring  out  with 
great  clearness  their  differential  diagnosis. 

From  the  New  York  Medical  Record. 

"  Special  attention  is  given  throughout  to  treatment,  and  the  discussion  of  controverted 
points  on  pathology,  etc.,  is  relegated  to  the  background.  The  key-note  is  the  idea  that  the  chief 
aim  and  object  of  surgery  at  the  present  day  is  to  assist  the  tissues  in  every  possible  way  in  their 
struggle  against  disease. 

"  From  such  a  standpoint  it  goes  without  saying  that  the  writer's  attitude  is  a  conservative 
one.  He  is,  however,  free  from  hesitancy,  and  shows  a  keen  appreciation  of  the  rapid  strides 
of  surgical  art  in  the  last  decade.  No  less  than  two  hundred  of  the  illustrations  were  drawn 
expressly  for  this  work.  It  has  all  the  conciseness  of  Druitt's  well-known  work,  and  the 
advantage  of  a  somewhat  more  extensive  description  of  certain  conditions  occurring  in  practical 
work." 
4®=A  complete  circular,  with  sample  pages,  press  notices,  etc.,  will  be  sent  free  upon  application. 


From  The  Southern  Clinic. 

"  We  know  of  no  series  of  books  issued  by  any  house  that  so  fully  meets  our  approval  as  these 
?  Quiz-Compends  ?.  They  are  well  arranged,  full,  and  concise,  and  are  really  the  best  line  of  text- 
books that  could  be  found  for  either  student  or  practitioner." 


BLAKISTON'S  ?QUIZ=COMPENDS? 

The  Best  Series  of  Manuals  for  the  Use  of  Students. 

Price  of  each,  Cloth,  $1.00.     Interleaved,  for  taking  Notes,  $1.25. 

JSl^  These  Compends  are  based  on  the  most  popular  text-books  and  the  lectures  of  prominent  professors, 
and  are  kept  constantly  revised,  so  that  they  may  thoroughly  represent  the  present  state  of  the  subjects  upon 
which  they  treat. 

4®=-  The  authors  have  had  large  experience  as  Quiz-Masters  and  attaches  of  colleges,  and  are  well 
acquainted  with  the  wants  of  students. 

4®"  They  are  arranged  in  the  most  approved  form,  thorough  and  concise,  containing  over  6oo  fine  illustra- 
tions, inserted  wherever  they  could  be  used  to  advantage. 

Jt^  Can  be  used  by  students  of  any  college. 

O*  They  contain  information  nowhere  else  collected  in  a  such  a  condensed,  practical  shape, 

ILLUSTRATED  CIRCULAR  FREE. 

No.  I.  HUMAN  ANATOMY.  Fifth  Revised  and  Enlarged  Edition.  Including  Visceral  Anatomy.  Can 
be  used  with  either  Morris's  or  Gray's  Anatomy.  117  Illustrations  and  16  Lithographic  Plates  of  Nerves  and 
Arteries,  with  Explanatory  Tables,  etc.  By  Samuel  O.  L.  Potter,  m.d.,  Professor  of  the  Practice  of 
Medicine,  Cooper  Medical  College,  San  Francisco;  late  A.  A.  Surgeon,  U.  S.  Army. 

No.  2.  PRACTICE  OF  MEDICINE.  Part  I.  Fifth  Edition,  Revised,  Enlarged,  and  Improved.  By 
Dan'l  E.  Hughes,  m.d.,  Physician-in-Chief,  Philadelphia  Hospital,  late  Demonstrator  of  Clinical  Medi- 
cine, Jefferson  Medical  College,  Philadelphia. 

No.  3.  PRACTICE  OF  MEDICINE.  Part  II.  Fifth  Edition,  Revised,  Enlarged,  and  Improved.  Same 
author  as  No.  7. 

No.  4.  PHYSIOLOGY.  Seventh  Edition,  with  new  Illustrations  and  a  table  of  Physiological  Constants. 
Enlarged  and  Revised.  By  A.  P.'  Brubaker,  m.d.,  Professor  of  Physiology  and  General  Pathology  in  the 
Pennsylvania  College  of  Dental  Surgery;  Demonstrator  of  Physiology,  Jefferson  Medical  College,  Phila- 
delphia. 

No.  5.  OBSTETRICS.  Fifth  Edition.  By  Henry  G.  Landis,  m.d.  Revised  and  Edited  by  Wm  H. 
Wei.ls,  m.d..  Assistant  Demonstrator  of  dbstetrics,  Jefferson  Medical  College,  Philadelphia.  Enlarged 
■*  47  Illustrations. 

No.  6.  MATERIA  MEDICA,  THERAPEUTICS,  AND  PRESCRIPTION  WRITING.  Sixth 
Revised  Edition  (U.S.  P.  1890).  By  Samuhi.  O.  L.  Potter,  m.d.  Professor  of  Practice,  Cooper  Medical 
College,  San  Fr.-incisco  :  late  A    A.  Surgeon,  U.  S.  Army. 

No.  7.  GYNAECOLOGY.  A  New  Book.  By  Wm.  H.  Wells,  m.d..  Assistant  Demonstrator  of  Obstetrics, 
Jefferson  College,  Philadelphia.     Illustrated. 

No.  8.  DISEASES  OF  THE  EYE  AND  REFRACTION.  Second  Edition.  Including  Treatment  and 
Surgery.     By  L.  Webster  Fox,  m  d.,  and  George  M.-  Gould,  m.d.    With  39  Formulae  and  71  Illustrations. 

No.  9.  SURGERY,  Minor  Surgery,  and  Bandaging.  Fifth  Edition,  Enlarged  and  Improved.  By 
Orvillh  Horwitz,  b.s.,  m.d..  Clinical  Professor  ot  Genito-Urinary  Surgery  and  Venereal  Diseases  in  Jef- 
ferson Medical  College;  Surgeon  to  Philadelphia  Hospital,  etc.     With  9S  Formula  and  71  Illustrations. 

No.  10.  MEDICAL  CHEMISTRY.  Fourth  Edition.  Including  Urinalysis,  Animal  Chemistry, Chemistry 
of  Milk,  Blood.  Tissues,  the  Secretion;,  etc  By  Henkv  Leffmann,  m.d.,  Professor  of  Chemistry  in 
Pennsylvania  College  of  Dental  Surgery  :ind  in  the  Woman's  Medical  College,  Philadelphia. 

No.  II.  PHARMACY.  Fourth  Edition.  Based  upon  Prof.  Remington's  Text-Book  of  Pharmacy.  By  F. 
E.  Stewart,  m.d.,  ph. g.,  late  Quiz-Master  in  Pharmacy  and  Chemistry,  Philadelphia  College  of  Pharmacy  ; 
Lecturer  at  Jefferson  Medical  College.     Carefully  revised  in  accordance  with  the  new  U.  S.  P. 

No.  12.  VETERINARY  ANATOMY  AND  PHYSIOLOGY.  Illustrated.  By  Wm.  R.  Ballou,  m  p.. 
Professor  of  Equine  Anatomy  at  New  York  College  of  Veterinary  Surgeons;  Physician  to  Bellevue  Dis- 
pensary, etc.     With  29  graphic  Illustrations. 

No.  13.  DENTAL  PATHOLOGY  AND  DENTAL  MEDICINE.  Second  Edition,  Illustrated.  Con- 
taining all  the  most  noteworthy  points  of  interest  to  the  Dental  Student  and  a  Section  on  Emergencies.  By 
Geo.  W.  Warren,  d.d.s..  Chief  of  Clinical  Staff,  Pennsylvania  College  of  Dental  Surgery,  Philadelphia. 

No.  14.  DISEASES  OF  CHILDREN.  Colored  Plate.  By  Marcus  P.  Hatfield,  Professor  of  Dis- 
eases of  Children,  Chicago  Medical  College. 

No.  15.  GENERAL  PATHOLOGY  AND  MORBID  ANATOMY.  91  Illustrations.  By  H.  New- 
berry Hall,  ph.g.,  m.d..  Professor  of  Pathology  and  Medical  Chemistry,  Chicago  Post-Graduate  Medical 
School. 

Price,  each,  $1.00.    Interleaved,  for  taking;  Notes,  $1.25. 

P.   BLAKISTON,  SON   &   CO.,   Publishers, 

IOI2  Walnut  Street,  Philadelphia. 


Published  Annually  for  44  Years. 


The  Physicians  Visiting  List. 

(LINDSAY  &  BLAKISTON'S. ) 
Contents.  —  Special  Revised  Edition  for  1895. 


CALENDAR,  1895-1896. 

TABLE  OF  SIGNS,  to  be  used  in  keeping  records. 

THE  METRIC  OR  FRENCH  DECIMAL  SYSTEM  OF 
WEIGHTS  AND  MEASURES. 

TABLE  FOR  CONVERTING  APOTHECARIES' 
WEIGHTS  AND  MEASURES  INTO  GRAMS. 

POSOLOGICAL  TABLE  (Meadows). 

DOSE  TABLE,  giving  the  doses  of  official  and  unofficial  drugs 
in  both  the  English  and  Metric  Systems.  Completely  re- 
written and  rearranged  for  1894  by  Dr.  George  M.  Gould. 

LIST  OF  NEW  REMEDIES,  1894. 

INCOMPATIBILITY  (Dr.  S.  O.  L.  Potter). 


POISONS  AND  ANTIDOTES. 

DISINFECTANTS. 

EXAMINATION  OF  URINE  {Based  upon   Tyson,  Eightn 

Edition). 
BRIGHT'S  DISEASE.  Differential  Diagnosis  of. 
DIAGNOSIS  AND  TREATMENT  OF  THE  SIMPLER 

DISEASES  OF  THE  EYE  (Dr.  George  M.  Gould). 
THE  ERUPTIVE  FEVERS,  Table  of. 
ASPHYXIA  AND  APNCEA. 
COMPLETE    TABLE    FOR    CALCULATING    THE 

PERIOD  OF  UTERO-GESTATION. 
COMPARISON  OF  THERMOMETERS. 


AND  THE  USUAL  BLANK  LEAVES  FOR  KEEPING  ACCOUNTS,  RECORDS.  ENGAGEMENTS, ETC. 


SIZES  AND  PRICES. 


REGULAR  EDITION. 

For  25  Patients  weekly.  Tucks,  Pockets  and  Pencil, 

50 


75 
100 


:  Vols. 


f  Jan.  to  June] 
I  July  to  Dec.  J 

.Vols-l-iT'.^ly"    . 
(July  to  Dec.  J 


INTERLEAVED  EDITION. 

For  25  Patients  weekly.      Interleaved,  Tucks  and  Pencil, 


^v-'-teioLr}" 


^I.OO 

1.25 

X.50 

2.00 
2.50 
3.00 


1-25 

1.50 


PERPETUAL  EDITION,  without  Dates. 

No.  I.  Containing  space  for  over  1300  names,  with  blank 
page  opposite  each  Visiting  List  page.  Bound 
in  Red  Leather  cover,  with  Pocket  and 
Pencil,  ..... 

No.  2.     Containing  space  for  2600  names,  with   blank 
page  opposite  each  Visiting  List  page.    Bound 
like  No.  1,  with  Pocket  and  Pencil, 
MONTHLY  EDITION,  without  Dates. 

No.  I.     Bound,  Seal  leather,  without  Hap  or  Pencil, 
gilt  edges. 

No.  2.  Bound,  Seal  leather,  with  Tucks,  Pencil,  etc., 
gilt  edges.  .  .  .  .  ' 


$1.25 


SPECIAL  SIZES  AND  BINDINGS  MADE  TO  ORDER. 


"  The  fact  that  this  Visiting  List  has  been  published  annually  for  forty  years  is  suffi- 
cient guarantee  of  its  excellence  and  popularity.  In  addition  to  the  visiting  list  proper, 
it  contains  easily-accessible  suggestions  upon  many  of  the  emergencies  that  may  arise  in 
a  physician's  practice,  as  when  he  is  too  far  from  home  to  learn  from  his  text-books  the 
antidote  for  a  poison  that  may  have  been  swallowed,  or  the  proper  method  of  resuscitating 
a  half-drowned  person.  True,  he  should  know  these  things,  but  who  does  not  occasion- 
ally forget,  when  he  most  wishes  to  remember  ?  There  are  also  dose-tables,  tahles  of  the 
metric  system,  a  list  of  new  remedies,  rules  for  examining  urine,  a  table  for  calculating 
the  period  of  pregnancy,  and  other  equally  useful  information.  The  arrangement  for 
entering  patients,  visits,  consultations,  etc.,  is  exceeding  simple,  and  the  whole  makes  a 
thin,  compact,  and  easily-carried  volume." — Medical  News,  Fhilada. 

l^'The  Perpetual  and  Monthly  Editions  can  be  commenced  at  any  time  and 
used  until  full. 

Jg^'This  is  a  plain,  systematic  method  of  keeping  a  record  of  visits ;    well  printed, 
strongly  bound,  durable,  convenient,  and  small. 

This  Visiting  List  is  published  in  November  of  each  year. 

P.  BLAKISTON,  SON  &  CO.,  PHILADELPHIA. 


